s

Arne Duinker, Irja Sunde Roiha, Heidi

Amlund, Lisbeth Dahl, Erik-Jan Lock,

Tanja Kögel, Amund Måge and Bjørn

Tore Lunestad

Nasjonalt institutt for ernærings- og sjømatforskning (NIFES)

18.03.2016

Potential risks posed by macroalgae for application as feed and food

- a Norwegian perspective

2016

Report

17. June 2016

National Institute of Nutrition and

Seafood Research (NIFES)

1

TABLE OF CONTENTS

1. Summary .............................................................................................................................. 2

2. Sammendrag ........................................................................................................................ 3

3. Introduction.......................................................................................................................... 5

4. Contaminants and biohazards: Content and implications in food and feed ............................. 6

Heavy metals and other elements ...................................................................................................... 6

1. Occurrence data ...................................................................................................................... 6

2. Comments to the occurrence data .......................................................................................... 9

3. Implications for food safety .................................................................................................. 11

4. Implications for feed safety ................................................................................................... 12

Iodine ................................................................................................................................................. 12

Persistent organic pollutants (POPs) ................................................................................................. 14

Toxins and anti-nutrients .................................................................................................................. 14

Radioactivity ...................................................................................................................................... 15

Micro-organisms ................................................................................................................................ 15

Microplastics ..................................................................................................................................... 18

Digestibility of seaweed carbohydrates. ........................................................................................... 18

5. Conclusions ......................................................................................................................... 19

6. Literature list ...................................................................................................................... 20

2

Macroalgae comprise a large and diverse group of organisms living predominantly in salt and brackish waters. Based on the colour of the dominating pigments of the macroalgae, they can coarsely be divided into brown algae (Phaeophyceae) comprising the perennials and kelps, green algae (Chlorophyceae) and red algae (Rhodophyceae).

The consumption of macroalgae is not recorded in dietary surveys and it is therefore difficult to estimate the intake of the different nutrients and non-nutrients in the population from macroalgae. So far, the amount of utilised macroalgae for direct consumption in Norway has been limited, but lately an increased interest in both the cultivation and harvest from wild stocks is seen.

The available occurrence data indicate that Norwegian macroalgae may contain elevated levels of inorganic arsenic, total arsenic and cadmium, while the levels of mercury and lead are low. High levels of inorganic arsenic and cadmium are particularly found in brown algae and may limit their use as food and feed ingredients. There are currently no regulations for macroalgae used as food. More occurrence data are needed to describe the seasonal variation of especially inorganic and total arsenic and cadmium in macroalgae from Norwegian waters.

The level of iodine in macroalgae is in general relatively high and brown algae seems to have the highest levels. Only a small intake of dried brown algae will contribute with an excessive iodine intake, however, the frequency of intake will be crucial in the evaluation of how this may affect the thyroid function. It is also important to assess the bioavailability of iodine and the loss of iodine during food processing (e.g. boiling). More knowledge about these factors are of importance when estimating the iodine intake and its effect on the thyroid function.

The levels of persistent organic pollutants in macroalgae are low compared to other foods, as expected due to low levels of fats. Data are however scarce.

Certain algae produce neurotoxins as secondary metabolites. There are no recorded poisoning related to macroalgae reported in Europe so far. Only a few studies describe toxins in European waters, and the levels reported are low and of no concern for human health. Poisoning have been reported, however, in Asia caused by blue-green algal epiphytes on macroalgae.

Macroalgae do accumulate radionuclides, but few studies focus on food safety and no levels of concern for food safety were found.

The surface of macroalgae form favourable habitats for microbes, where the load and diversity differ between the various algal species and may differ from the surrounding water communities, indicating algae-microbe interactions. Such interactions seem to be important for host health and infection defence. Most studies concerning microbial communities associated with macroalgae have an ecologic focus, describing the numbers, diversity and role of bacteria on the surfaces of the algae. Based on the studied literature, the question regarding possible enhanced survival of faecal bacteria and potential human pathogens associated to macroalgae remain largely unresolved. Some of the bacteria found on macroalgae have a potential as human pathogens, or could give challenges during processing and storage, but the importance of algae in feed or food borne disease cannot be expected to be higher than for other non-filtering marine organisms used for such purposes, including fish.

Microplastics, defined as plastic particles smaller than five millimeters, are now common at all levels of the marine environment. Such particles are prone to accumulation of organic contaminants, which again can adsorb onto macroalgae, potentially introducing the particles and their associated contaminants into animals feeding on them, including humans. The possible implications of this are however not known.

1. SUMMARY

3

Macroalgae contain different polysaccharides compared to terrestrial plant. The energy content for human and animal nutrition seems to be low, but is not very well documented. This might be positive in the perspective of too high energy density in some human diets. However in a perspective of feed the lack of energy availability from polysaccharides might be a problem.

Makroalger utgjør en sammensatt gruppe organismer som i hovedsak er å finne i sjø eller brakkvann. På bakgrunn av de mest dominerende pigmentene, deles makroalger grovt inn i brunalger (Phaeophyceae) som inkluderer tang og tare, grønnalger (Chlorophyceae) og rødalger (Rhodophyceae).

Data for inntak av makroalger er ikke inkludert i kostholdsstudier, og det er derfor vanskelig å estimere mengden næringsstoffer og andre stoffer enn næringsstoffer makroalgene står for i kostholdet. Så langt har det bare blitt benytte mindre mengder makroalger til direkte humant konsum, men i det siste har en sett økt interesse for dyrkning og høsting fra ville populasjoner.

Tilgjengelig informasjon om metaller i norske makroalger indiker at en kan finne forhøyede konsentrasjoner av uorganisk arsen og kadmium, særlig hos brunalger. Konsentrasjonene av kvikksølv og bly er lave i makroalger. De høye konsentrasjonene av arsen og kadmium kan sette begrensinger for bruk av makroalger til mat og som fôringrediens. Det mangler fremdeles undersøkelser for å karakterisere forekomst av arsen og andre tungmetaller i norske makroalger på en tilfredsstillende måte.

Konsentrasjon av jod i makroalger er forholdsvis høy og brunalger synes å ha de høyeste nivåene. Selv et lavt inntak av tørkede brune alger vil gi et jodbidrag over anbefalt dagsdose. Hvor ofte det inntas makroalger er imidlertid avgjørende for hvordan dette kan påvirke skjoldbruskkjertelens funksjon. Det er også viktig å vurdere biotilgjengeligheten til jod og tapet av jod under prosessering av mat (f.eks. koking). Det er behov for mer kunnskap om disse faktorene og hvordan dette påvirker både jodinntaket og skjoldbruskkjertelens funksjon.

Makroalger er svært lite fettrike. Som forventet er konsentrasjoner av persistente organiske miljøgifter i makroalger lavere enn det en finner hos andre organismer som kan brukes til mat og fôr.

Noen alger produserer nervegifter som sekundære nedbrytningsprodukter. Det er så langt ikke rapportert om forgiftninger fra slike giftstoffer i Europa. Et fåtall studier beskriver toksiner i europeiske farvann, men nivåene som er rapportert er lave. Forgiftninger forårsaket av blågrønnalger som vokser som epifytter på makroalger er rapportert fra Asia.

Ved gjennomgang av litteraturen, er det ikke funnet informasjon om at makroalger kan representere en utfordring med tanke på radioaktivitet.

Makroalger er et yndet habitat for mikroorganismer og store mengder bakterier lever på overflaten av algene. Mengden og sammensetningen varierer mellom de ulike algeartene og kan være forskjellig fra vannet de lever i, noe som indikerer spesifikke alge-bakterie interaksjoner. Denne vertsspesifikke diversiteten ser ut til å være viktig for algens helse og infeksjonsforsvar. De fleste studier tar for seg

2. SAMMENDRAG

4

mikrobielle samfunn assosiert med makroalger i et økologiske perspektiv. Der er svært få publikasjoner knyttet til humanpatogene bakterier fra makroalger fra nordlige farvann, eller som tar for seg problemstillingen knyttet til alger og bakterier fra fekal forurensning. Literturstudien viser at spørsmål knyttet til overlevelse av tarmbakterier og human patogener assosierte med makroalger stort sett er ubesvarte. Det kan konkluderes med at det på overflaten av makroalger finnes store mengder bakterier og at noen av disse potensielt kan skape problem ved prosessering eller ikke-optimal lagring. Betydning av disse kan ikke ses på som større enn for andre ikke-filtrerende organismer som fisk.

Mikroplast defineres som partikler mindre enn 5 mm. Slike partikler er nå vanlige i det marine miljøet. Mikroplast vil lett knytte organiske forurensningsstoffer til seg, og kan siden bli oppkonsentrert på overflaten av makroalger som så kan bringe stoffene over i mat eller fôr. Når dyr som strandsnegl beiter på overflaten av makroalger, vil mikroplast og organiske forurensningsstoff kunne komme inn i næringskjeden. Hvilken risiko dette kan medføre er ukjent.

Makroalger inneholder uvanlige polysakkarider sammenlignet med det er finner i terrestrisk planter, og næringsverdien av disse karbohydratene er til dels lav eller lite kjent. Fra et folkehelseperspektiv kan dette være fordelaktig da det kan gi redusert energitetthet. Fra at dyrefôrperspektiv kan dette representere et problem.

5

The Norwegian Food Safety Authority (NFSA) have asked NIFES for an assessment on potential negative effects on the health of humans and animals posed by the consumption of macroalgae harvested from Norwegian waters. This report summaries the current available knowledge on organic and inorganic contaminants, naturally found toxins and anti-nutrients in certain macroalgae, micro-organisms of health concern and the effects of microplastics in the environment, as well as aspects of digestibility of algal carbohydrates.

Macroalgae comprise a large and diverse group of plants living predominantly in salt and brackish waters. The macroalgae are, in contrast to most land-living plants, not differentiated into root, steam and leaf. Based on the colour of the dominating photosynthetic pigments, these algae can coarsely be divided into the brown algae (Phaeophyceae) comprising the perennials and kelps, green algae (Chlorophyceae) and red algae (Rhodophyceae). Although we use the term plants here for simplicity, it should be noted that only the green algae are classified together with land plants in the phylum Plantae, whereas the red and brown algae are not (La Barre, Potin et al. 2010). Depending on different regional human or agricultural habits, these algae have traditionally been used for food, as feed or soil fertilizers. In addition, several industrially produced compounds, as alginate and carrageen, are utilized as thickeners, gelling agents, stabilizers and emulsifying agents in a variety of food and feed. The refined products from algae are however not evaluated or discussed in this report. The most relevant species for farming, commercial or public harvest are listed in Table 1.

Table 1. List of relevant species of macroalgae for direct consumption in Norway.

Norwegian English Latin

Bro

wn

p

er-

enn

ials

Grisetang Rockweed, egg wrack Ascophyllum nodosum

Blæretang Bladderwrack Fucus vesiculosus

Sauetang Channeled wrack Pelvetia canaliculata

Bro

wn

an

nu

als

Martaum, åletang Sea lace Chorda filum

Remtang Sea spaghetti Himanthalia elongata

Ke

lp

Sukkertare Sugar kelp Saccharina latissima

Fingertare Oarweed Laminaria digitata

Butare Alaria, winged kelp Alaria esculenta

Stortare Tangle Laminaria hyperborea

Gre

en a

lgae

Havsalat Sea lettuce Ulva lactuca

Tarmgrønske Gut weed, mermaids hair Enteromorpha intestinalis

Pollpryd Sponge seaweed Codium fragile

Red

alg

ae Søl Dulse, dillisc Palmaria palmata

Fjærehinne Laver Porphyra purpurea

Grisetangdokke Wrack siphon weed Polysiphonia (Vertebrata) lanosa

Krusflik Irish moss Chondrus crispus

3. INTRODUCTION

6

Several aspects of the macroalgae biology may influence the levels of contaminants. The chemical composition of macroalgae differs from other types of seafood in the high content of specific polysaccharides in the structural components of the algae. The types of polysaccharides differ between brown, red and green algae, with alginate in brown algae as the most utilised one. The polysaccharides have metal-binding characteristics that may affect both the levels of metals and the availability of these metals through the digestion processes. The algae have generally low levels of lipids, and thus low levels of organic, lipid-soluble contaminants is expected. The shape of the fronds on the other hand, with a large surface area in contact with the water, will facilitate uptake of such contaminants.

So far, the amount of macroalgae utilised for direct human consumption in Norway has been limited, but lately an increased interest in the cultivation and harvest from wild stocks is seen. An overview of the most relevant macroalgae in Norway are given in Table 1. The increased interest for algal cuisine is also relatively new in the rest of Europe, and so far, no regulations with maximal levels for contaminants exists for seaweed as food in Norway or the EU. Further, there is increasing interest on marine algae in animal feed, especially since the Norwegian demands for ingredients for fish feed is growing. The safety of these new food and feed materials is however not elucidated and this is subject for discussions in the EU committees, in particular regarding arsenic, cadmium and iodine.

Heavy metals and other elements

1. Occurrence data

Some recent studies on elements in macroalgae harvested in Norway have been performed and some are ongoing, and the data are compiled in Tables 2 to 7. The data includes published information (Duinker 2014), as well as unpublished data from an ongoing research project (AquaFly, NIFES ).

The level of copper, iodine, selenium and zinc in macroalgae collected in Norway are summarized in Tables 2 and 3. These elements are important nutrients but can be toxic at elevated levels. As can be seen, the levels of copper and selenium are low, ranging from 1.6 to 17 mg/kg dry weight (d.w.) and from 0.02 to 0.53 mg/kg d.w., respectively. The levels of zinc are generally also low, but rather high in some species (Table 2). High levels of zinc were found in the red algae Vertebrata lanosa (81 mg/kg d.w.), the green algae Ulva lactuca (176 mg/kg d.w.) and the brown algae Laminaria digitata (70 mg/kg d.w.) and Saccharina latissima (138 mg/kg d.w.) (Table 2). Data collected in an ongoing research project supports these findings, as higher levels of zinc were found in red and brown algae (Table 3). Based on the data collected so far, copper, selenium and zinc levels in macroalgae do not pose a risk when applied as food and feed.

Table 2. Analysed concentrations of copper, iodine, selenium and zinc in selected macroalgae harvested in Norway. All concentrations are given in mg/kg dry weight (d.w.).

Species Copper Iodine Selenium Zinc Reference

4. CONTAMINANTS AND BIOHAZARDS: CONTENT AND

IMPLICATIONS IN FOOD AND FEED

7

Red algae Palmaria palmata

4.9 260 0.14 29 Mæhre et al. 2014

- 57-414 0.06-0.15 24-40 Duinker 2014

Polysiphonia lanosa

8 1300 0.53

81

Mæhre et al. 2014

Green algae

Cladophora rupestris

17 63 0.066 30 Mæhre et al. 2014

Enteromorpha intestinalis

4.9 130 0.028 25 Mæhre et al. 2014

Ulva lactuca 6 21 0.049 8 Mæhre et al. 2014

- 60-288 0.04-0.12 10-176 Duinker 2014

Brown algae

Alaria esculenta

2.4 220 0.041 49 Mæhre et al. 2014

Laminaria digitata

1.6 3100 0.021 24 Mæhre et al. 2014

- 2136-4375 0.02-0.04 34-70 Duinker 2014

Laminaria hyperborea

1.7 3500 0.033 22 Mæhre et al. 2014

Fucus vesiculosus

1.8 130 0.03 26 Mæhre et al. 2014

Pelvetia canaliculata

2.6 210 0.035 31 Mæhre et al. 2014

Saccharina latissima

- 2103-3378 0.04-0.06 24-138 Duinker 2014

1655 Lunig and Mortensen 2015

Table 3. Concentrations of copper, iodine, selenium and zinc in selected macroalgae harvested in Norway as a part of the ongoing AquaFly project at NIFES. Mean concentrations are given in mg/kg d.w. ± SD, with min-max values in parenthesis.

Copper Iodine Selenium Zinc n

Red algae* 7.0 ± 2.2 (3.7-10)

134 ± 111 (14-340)

0.13 ± 0.08 (0.05-0.29)

43 ± 20 (23-72)

8

Green algae** 7.5 ± 1.8 (5.7-10)

190 ± 196 (43-480)

0.43 ± 0.34 (0.14-0.76)

16 ± 4.4 (12-21)

4

Brown algae*** 2.2 ± 1.0 (0.77-3.9)

1438 ± 2624 (59-10000)

0.10 ± 0.11 (0.02-0.49)

43 ± 30 (16-120)

15

*Chondrus crispus, Furcellaria lumbricalis, Mastocarpus stellatus, Palmaria palmata, Porphyra dioica, Porphyra purpurea, and Porphyra umbilicalis

**Cladophora rupestris, Ulva intestinalis and Ulva lactuca

***Alaria esculenta, Ascophyllum nodosum, Chordaria flagelliformis, Fucus serratus, Fucus spiralis, Fucus vesiculosus, Halidrys siliquosa, Himanthalia elongata, Laminaria digitata, Pelvetia canaliculata, and Saccharina latissima

8

The levels of cadmium, mercury, lead and arsenic in macroalgae collected in Norway are summarized in Tables 4 and 5. The levels of mercury and lead are low in all analysed species. The level of cadmium is low (0.08 – 0.22 mg/kg d.w.) in green algae, while for red and brown algae the content of cadmium varies from 0.1 to 3.8 mg/kg d.w. (Table 4). The highest concentrations were found in the red algae Vertebrata lanosa and the brown algae Alaria esculenta, Laminaria digitata and Laminaria hyperborea. Data collected in an ongoing research project supports these findings, as low levels of cadmium were found in green algae and higher levels were found in red and green algae (Table 5). The levels measured were comparable for all three datasets. The levels of arsenic were high, ranging from 4.9 to 107 mg/kg d.w. in all samples (Table 4). Higher levels of arsenic were found in brown algae, where the concentration ranged from 28 to 107 mg/kg d.w., with highest levels found in L. digitata (Table 4). The concentration of inorganic arsenic were determined in a few samples; the level of inorganic arsenic seems to be low, but one samples of the brown algae L. digitata contained as high as 7.7 mg/kg d.w. (Table 4), whereas other species were below 0.12 mg/kg d.w. (Duinker 2014). These observations are supported by data collected in an ongoing research project. Brown algae contained higher levels of total arsenic than red and green algae (Table 5). However, the level of inorganic arsenic (0.05 – 2.4 mg/kg d.w.) was low compared to total arsenic (Table 5). The levels measured were comparable for all three datasets.

Table 4. The levels of cadmium, mercury, lead and arsenic in selected macroalgae collected in Norway. Concentrations are given in mg/kg d.w.

Species Cadmium Mercury Lead Arsenic Inorganic arsenic

Reference

Red algae

Palmaria palmata

0.48 0.005 - 10 - Mæhre et al. 2014

0.12-0.26 <0.005-0.01 0.09-1.12 9-12 0.05 Duinker 2014

Polysiphonia lanosa

3.8 0.01 - 9.3 - Mæhre et al. 2014

Green algae

Cladophora rupestris

0.091 0.006 - 9.4 - Mæhre et al. 2014

Enteromorpha intestinalis

0.12 0.014 - 4.9 - Mæhre et al. 2014

Ulva lactuca 0.092 0.005 - 7.9 - Mæhre et al. 2014

0.08-0.22 0.00-0.01 0.18-0.23 6-13 0.12

Duinker 2014

Brown algae

Alaria esculenta

3.4 <0.005 - 48 - Mæhre et al. 2014

Laminaria digitata

0.1 0.006 - 64 - Mæhre et al. 2014

0.33-1.94 0.01-0.02 0.08-0.22 73-107 0.1-7.7 Duinker 2014

Laminaria hyperborea

0.48 0.007 - 55 - Mæhre et al. 2014

Fucus vesiculosus

1.2 0.011 - 41 - Mæhre et al. 2014

9

Pelvetia canaliculata

0.48 0.047 - 28 - Mæhre et al. 2014

Saccharina latissima

0.28-0.46 0.01-0.02 0.19-0.72 61-66 0.03-0.07 Duinker 2014

Maximum level

Feed 0.5 (1*) 0.1 (0.2*) 5 2 (10*) - **

Feed material 1 0.1 10 40 - **

* Fish feed, ** Commision directive 2002/32/EC and amendments

Table 5. The levels of cadmium, mercury, lead and arsenic in selected macroalgae collected in Norway as a part of the AquaFly project. Concentrations are given in mg/kg d.w., mean ± SD (min-max) Mean concentrations are given in mg/kg dry weight (d.w.) ± SD, with min-max values in parenthesis.

Species Cadmium Mercury Lead Arsenic Inorganic arsenic

n

Red algae* 0.73 ± 0.00 (0.07-3.1)

0.01 ± 0.00 (<0.005-0.01)

0.26 ± 0.18 (0.05-0.58)

15 ± 6.8 (6.4-24)

0.09 ± 0.09 (0.01-0.24) 8

Green algae** 0.18 ± 0.06 (0.12-0.27)

0.01 ± 0.00 1.5 ± 1.1

(0.36-3.0) 8.6 ± 2.2 (6.4-11)

0.28 ± 0.17 (0.05-0.44) 4

Brown algae*** 1.1 ± 1.5 (0.03-5.9)

0.01 ± 0.01 (<0.005-0.04)

0.26 ± 0.26 (0.05-1.1)

41 ± 26 (19-120)

0.33 ± 0.64 (0.02-2.4) 15

*Chondrus crispus, Furcellaria lumbricalis, Mastocarpus stellatus, Palmaria palmata, Porphyra dioica, Porphyra purpurea, and Porphyra umbilicalis

**Cladophora rupestris, Ulva intestinalis, and Ulva lactuca

***Alaria esculenta, Ascophyllum nodosum, Chordaria flagelliformis, Fucus serratus, Fucus spiralis, Fucus vesiculosus, Halidrys siliquosa, Himanthalia elongata, Laminaria digitata, Pelvetia canaliculata, and Saccharina latissima

2. Comments to the occurrence data

There are few analytical data on metals in macroalgae from Norwegian waters thus far, and there is particularly need for more data on the commercial species as Laminaria hyperborea from wild harvest, as well as farmed Saccharina latissima and Alaria esculenta. More data are also warranted on geographical and seasonal variations.

Metal concentrations in macroalgae varies between species. However, within a species variations in metal concentrations appear to be site-specific, related to seaweed growth rates and differs between different parts of the seaweed. These growth rates are affected by ambient environmental conditions, as well as factors enhancing or reducing accumulation, such as temperature, light, nutrients and salinity (Morrison, Baumann et al. 2008), and causes a seasonal variation of metal concentrations in macroalgae.

10

Location

Myklestad et al. (1978) described the effect of water zinc and copper concentrations at two locations, Hardangerfjord and Trondheimsfjord, on accumulation in Ascophyllum nodosum. Ascophyllum is perennial and it appears that metal concentrations increase with increasing age of the algae (Table 6). At that time, inner Hardangerfjorden, was highly contaminated by several heavy metals (Julshamn et al., 2001) It is assumed that the fast growth of the younger parts dilute the metal concentrations.

Table 6. Metal concentrations in A. nodosum from Hardangerfjord as a function of age. The higher the internode number the older the part of the algae. All concentrations are given in mg/kg d.w.

In the same study, A. nodosum was transfered from Hardangerfjord to Trondheimfjord. Metal concentration, exemplified with zinc, in inner Hardangerfjord was at the time between six and 50 times higher compared to Trondheimsfjord, and subsequent metal concentrations in A. nodosum was 10 times higher in Hardangerfjord compared to Trondheimsfjord. After the transfer from Hardangerfjord to Trondheimsfjord, the metal concentrations in A. nodosum decreased. The younger the internode the more pronounced the decrease was. A similar pattern was seen for mercury and in a lesser extent for lead (Table 7). A similar observation has been made for Saccharina latissima sampled at Lindesnes were lower levels of cadmium were found in the tip than at the stem (Duinker 2014). In the case for the annual kelp species, however, the tip represents the older part and the growth zone near the stem the younger parts, as opposed to what is seen in the perennial A. nodosum.

Table 7. Zinc content in different age groups of A. nodosum as a function of growth locality. All concentrations are given in mg/kg d.w.

Zn Cu Pb Cd Hg

Tips 1000 20 11 3.5 0.33

Internode 1 1710 24 13 6.3 0.50

Internode 2 2206 58 18 6.3 0.87

Internode 3 2708 59 24 7.3 1.16

Internode 4 2973 56 33 7.7 1.43

Internode >4 3597 82 54 7.3 4.48

Locality

Hardanger Trondheim Trondheim (transplant from Hardanger)

Age groups July Oct July Oct May July Sept Oct

Tips 900 1100 70 90 - 130 140 100

New vesicle 1130 1430 120 130 840 320 295 240

Internode 1 2050 1650 180 155 1710 840 560 515

Internode 2 2660 2090 230 230 2380 1750 1210 1050

Internode 3 3390 2640 240 265 2710 1950 2060 1430

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Seasonal variability - environmental factors

The uptake and availability of metals in the water are related to factors like salinity (Struck, Pelzer et al. 1997), pH (Gutknecht 1963), temperature (Munda 1979) and irradiance (Gutknecht 1963) creating a diurnal as well as a seasonal pattern (Stengel, Macken et al. 2004).

Seasonal changes in levels of different metals followed a seasonal pattern in Ulva sp., with lowest metal concentrations found in summer plants and maximum values in autumn/winter plants. This is most likely caused by a dilution effect due to growth during favourable periods and in winter to a large decrease in metabolic rates (Villares, Puente et al. 2002).

In A. nodosum concentrations of both Cu and Fe in apical tissue of A. nodosum exhibited more than two-fold changes between October and February, but there were contrasting trends for the two metals, as Cu concentrations decreased and Fe concentrations increased (Stengel, McGrath et al. 2005). A reduction in the concentration of cadmium from early to late spring was seen in macroalgae (Laminaria digitata, Palmaria palmata and Ulva lactuca) growing at Lindesnes (Duinker 2014). Seasonal fluctuations in metal concentration of marine algae are mainly considered a result of seasonal growth patterns. However, contrasting data have been published on the relationship between different tissue concentrations of different metals and growth rate. Accumulation of essential elements (e.g. Cu, Fe, Mn) increased during periods of fast growth, but less accumulation occurred during slow growth of Ulva fasciata (Rice and Lapointe 1981). Uptake of metals, such as Cd and Cu, during kelp culture decreased as growth increased (Markham, Kremer et al. 1980), (Stengel, McGrath et al. 2005).

Some of the variations in metal concentrations between different plants may be caused by epiphytes rather the macroalgae themselves. Moreover, different parts of the plants can have different concentrations of heavy metals, e.g. differences between stems and tips of various brown seaweed species (Stengel and Dring 2000; Stengel, McGrath et al. 2005).

Specific compounds in seaweed that bind metals

Presence of components of alginic acid (Vreeland 1972) and metal-cheating polyphenols, have been shown to determine binding affinities to metals in macroalgae. In red algae, variations in metal accumulation can be due to antagonistic effects of different polyvalent cations binding to sulphydryl groups of carageenan and sulphated galactans of agar (Paskinshurlburt, Tanaka et al. 1976). Also, Zn uptake by L. digitata in the laboratory was reduced in the presence of Cd or Cu. Differences in alginic acid compositions may alter the metal binding properties of brown algae.

3. Implications for food safety

The European food legislation aims to protect the consumer and sets maximum permitted levels for a range of contaminants in foodstuffs (Commission Regulation (EC) 1881/2006 and amendments). Below is a summary of current maximum levels (wet weight) for foodstuffs. For cadmium and lead, there are maximum levels for vegetables, but seaweed are excluded from these maximum levels. For cadmium, lead and mercury there are maximum levels for food supplements that also apply for macroalgae. They are 3.0, 3.0 and 0.1 mg/kg wet weight, respectively. For cadmium it is specified that the maximum level applies to “Food supplements consisting exclusively or mainly of dried seaweed, products derived from seaweed, or of dried bivalve molluscs”. There are currently no maximum levels for arsenic in vegetables or food supplements.

The levels of cadmium, mercury and lead in algae collected in Norway are low (Tables 4 and 5), and below the current maximum levels for these elements in food supplements.

There are currently no maximum level of arsenic in vegetables or food supplements. However, the elevated levels of inorganic arsenic in some species of seaweed may be of concern. In 2015, the Superior Health Council of Belgium conducted a risk assessment of the exposure to inorganic arsenic

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though the consumption of edible algae, i.e. macroalgae. They recommend that the consumption of Hijiki (a non-European species known to contain high levels of inorganic arsenic) should be avoided, and that the consumption of other algae should be limited to 7 g dried material per day (the Superior Health Council of Belgium, 2015). The dietary exposure to inorganic arsenic in the general European population is high (EFSA 2009, 2014), and consumption of algae with a high level of inorganic arsenic will lead to an additional exposure. Seaweed contains inorganic arsenic and organic forms of arsenic, mainly arsenosugars. Little is known of the toxicity of arsenosugars.

4. Implications for feed safety

The European feed legislation aims to protect animals, the consumer and the environment, and sets maximum permitted levels for a range of undesirables substances in feed ingredients and complete feedingstuffs (Commission Directive 2002/32/EC and amendments). Below is a summary of current maximum levels (12% moisture content) for feed materials and feed. The maximum arsenic level in feed materials from seaweed and products thereof is 40 mg/kg. The maximum arsenic level in feed is 2 mg/kg, and 10 mg/kg for fish feed. The Directive recognises that inorganic arsenic is the most toxic arsenic form and that marine feed ingredients mainly contain organic arsenic compounds. The maximum levels are set for the level of total arsenic, not inorganic arsenic. In addition, authorities can request documentation showing that the level of inorganic arsenic in macroalgae and products thereof, and in marine feed ingredients are below 2 mg/kg. For cadmium and lead, the current maximum permitted level in fish feed is 1 and 5 mg/kg, respectively, while for feed ingredients it is 1 (feed materials of vegetable origin) and 10 mg/kg, respectively. The current maximum level of mercury in fish feed and marine feed ingredients are 0.1 and 0.2 mg/kg, respectively.

Algae collected in Norway contains levels of mercury and lead that are below the current maximum levels. The levels of cadmium in some of the analysed algae exceeds the current maximum level of 1 mg Cd/kg feed (12% moisture content), and this limits the use of some macroalgae as a feed ingredient.

Red and green algae contain levels of arsenic that are below the current maximum level of 40 mg As/kg feed (12% moisture content) (Tables 4 and 5). Most of the analysed samples of brown algae contained levels of arsenic exceeding the current maximum limit, and this limits their use as a feed ingredient. There is limited data on the occurrence of inorganic As in Norwegian seaweed (Tables 4 and 5). Available data suggest that the levels of inorganic arsenic are low, but may be elevated in the brown algae Laminaria digitata. Levels of inorganic arsenic exceeding 2 mg/kg (12% moisture content) limits the use of macroalgae as a feed ingredient.

Based on the data collected so far, copper, selenium and zinc levels in macroalgae do not pose a risk for the use of macroalgae as feed or feed ingredient.

Iodine Iodine is an essential micronutrient required for the synthesis of the thyroid hormones triiodothyronine (T3) and thyroxine (T4). As iodine intake is important for the activity of the normal thyroid gland, the iodine intake of a population should be brought to the level at which iodine deficiency disorders are avoided (Laurberg, Nøhr et al. 2000).

Iodine is a non-metallic element and elemental iodine can exist in oxidation stages ranging from -1 to +7, but the main oxidation state is -1 as iodide.

The healthy human adult body contain approximately 15-20 mg iodine, of which 70-80% is present in the thyroid gland. Ingested inorganic iodine and iodate are reduced to iodine and almost completely absorbed from all levels of the gastrointestinal tract. Most of the iodine is transported to the thyroid

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gland and transforms through a series of metabolic steps into T3 and T4. Iodine also exist in the thyroid gland as inorganic iodine, monoiodotyrosin (MIT), diiodtoyrosin (DIT), polypeptides containing thyroxine and thyroglobulin.

The main source of iodine in humans is food, but the iodine concentration of different foodstuffs varies considerably. ). Determination of the iodine content in Norwegian foods shows that seafood, milk and dairy products, as well as eggs have the highest iodine concentration (Dahl, Johansson et al. 2004).The highest iodine content is found in foods of marine origin. Iodine in fish is reported in the range of 30 to 3500 µg/kg wet weight. Macroalgae are particularly high in iodine and concentrations are 100 to 1000 times higher than found for fish (NNR 2014, Mæhre et al. 2014). Our own data shown in tables 2 and 3 confirm this and values as high as with up to 5 000 mg/kg dry weight, and even 10 000 have been found in L. digitata (Lock unpublished data). These values poses challenges that must be further adressed.

The intake of iodine from macroalgae is difficult to estimate since such data are not collected in dietary surveys. However, if a small amount of seaweed such as dried brown algae is consumed, the risk of having an excess iodine intake is substantial. In the study by Mæhre et al. (2014) and in the report from Duinker (2014), iodine in samples of different common macroalgae species in Norway were determined (Table 2). According to these analyses, the levels of iodine are highest in brown algae, but it should be noted that the variation within the same species is large and the levels between different groups of algae (brown, green and red) varies considerably. According to the literature, season, salinity of the water, depth, water temperature, which part of the seaweed used, age of the seaweed and post-harvest storage conditions are all factors that affect the iodine content (Teas, Pino et al. 2004). In addition, food preparation and cooking methods will also be factors in determining the final iodine content (Teas, Pino et al. 2004).. Results from a study showed that the level of iodine was reduced by 70% after five minutes of boiling in water (Lüning and Mortensen 2015). The bioavailability of iodine is also of interest. In a cross over study from UK the bioavailability and impact of 2 week daily seaweed supplementation (potassium iodide and seaweed; 712 µg iodine/day) among non-pregnant women (n=22) were tested (Combet, Ma et al. 2014). They reported increased 24h iodine excretion, however, the increase differed between the iodine sufficient and the iodine insufficient groups of women; meaning that the women with the lowest iodine level increased mostly. The level of serum thyroid stimulating hormone (TSH) also increased in the groups with the exception of two women having concentrations exceeding the normal range. One important and interesting finding was the lower excretion of iodine per hour after seaweed intake and lower maximum peak compared to the salt. This indicate that the bioavailability of iodine from seaweed was lower compared to the iodine intake from potassium iodide (Combet, Ma et al. 2014). The Norwegian Nutrition Council has recently launched a report about the iodine situation in Norway and recommends that the use of dried seaweed products should be used with caution when the iodine level is unknown or if the level is very high as the daily iodine intake should not exceed 600 μg/day.

The recommended daily intake of iodine varies depending on age of the subject. Recommended intake is 150 µg/day for adults and children of 10 years or older according to Norwegian, Nordic and WHOs recommendations (NNR 2014). Recommended daily iodine intake levels are set at 90 µg for children of 2 to 5 years, and 120 µg for children of 6 to 9 years. For pregnant women the recommendation is 175 µg/day and for lactating women 200 µg/day. The lowest recommended daily intake of iodine for adults is 70 µg/day. The safe upper level for adults is proposed to be 600 µg/day for adults according to the Nordic nutrition recommendations (NNR 2014) and the Scientific Committee on Food (SCF 2002). Proposed upper level of iodine intake for children 1-3 years, 4-6 years, 7-10 years, 11-14 years and 15-17 years is 200, 250, 300, 450, 500 µg/day, respectively (SCF 2002).

Excess iodine is known to affect thyroid function, and in predisposed individuals, even a moderately increased iodine intake may cause hypothyreosis or hyperthyreosis (Jørgensen and Svindland 1991). An iodine intake in excess of 2 mg/day can cause sensitivity reactions such as rhinitis, nasal congestion,

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swollen salivary glands, headache, and acne like skin changes (NNR 2014). A high intake of iodine from e.g. drugs, certain types of algae or supplements in amounts corresponding to 1 mg up to 10 mg iodine/day has resulted in increased incidence of iodine goitre, in certain cases with hyperthyroidism or myxoedema (NNR 2014). Persons with a normal thyroid function can in general tolerate prolonged consumption of iodine up to 1 mg/day, but even a moderately increased iodine intake of up to 300 µg/day may cause hypothyreosis or hyperthyreosis. The thyroid is also shown to return to normal function within two-three months after cessation of the intake of seaweed or iodine supplement (Jørgensen and Svindland 1991). Chronic intake of moderate or large doses of iodine decrease the serum level of thyroid hormones and increases TSH levels (SCF 2002).

Persistent organic pollutants (POPs) The POPs are organic, lipid soluble pollutants including dioxins and PCBs. Macroalgae contain very little fats and it is therefore rather unlikely that the fat soluble pollutants (POPs) should accumulate to high levels. On a global basis, there are few data on dioxins and PCBs in seaweed. Macroalgae have in general lower concentrations of PCBs than other foods (Moon, Lee et al. 2005) and dioxin concentrations in Porphyra yessoensis and Eisenia bicyclis were 50 times lower than phytoplankton dominated by diatoms (which was higher than zooplankton) (Okumura, Yamashita et al. 2004). Few data are available with concentration of identified congeners of dioxins and PCBs. Okumura et al. (2004) found low levels of sum TEQWHO1998 dioxins and dioxin-like PCBs in Porphyra yessoensis and Eisenia bicyclis with 0.00027 and 0.0013 pg/g ww, respectively. Hashimoto and Morita (1995) found higher values with sum TEQWHO1998 dioxins and dioxin-like PCBs of 0.015-0.14 pg/g ww in Eisenia bicyclis and 0.33-0.79 in Undaria pinnatifida. However, all these concentrations are well below the regulatory limit for fish and other seafood animals.

Toxins and anti-nutrients Some macroalgae may produce or be a carrier of toxins of relevance for food and feed safety and in some instances also interesting for therapeutic value.

The presence of pinnatoxin in Norwegian S. latissima were most likely due to the presence of epiphytic benthic dinoflagellates attached to the kelp. The concentrations were low, however, making a poisoning unlikely, and 10-100 fold higher concentrations were found in shellfish (Iglesia, del Río et al. 2014).

Among the rare poisonings that have been described after intake of macroalgae, are intoxication from aplysiatoxin and debromoaplysiatoxin most probably derived from epiphytic blue-green algae on Gracilaria from Hawaii (Nagai, Yasumoto et al. 1996) .

Three different classes of compounds have been identified in poisonings with species in the genus Gracilaria. They are prostaglandin E-2 from G. verrucosa in Japan, aplysiatoxins and related compounds from G. coronopifolia in Hawaii, and polycavernosides from G. tsudai in Guam (Higa and Kuniyoshi 2000).

Sato et al. (1996) and references therein described Kainic acid and domoic acid in japan, found in red and green algae, but not brown algae. No toxic levels or intoxications were reported, and probably none of these species are found in Europe.

Seaweeds contain antinutrients as protective substances against grazing. Several publications describe effects of these substances as for instance polyphenols, on fish (Van Alstyne and Paul 1990). However, when searching for negative effects of polyphenols on humans, the literature is dominated on medical

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uses and their anti-oxidant or anti-cancer (Brown et al 2014). We have not been able to find publications documenting negative effects of antinutrients from seaweeds.

Certain species of macroalgae have been used in medicine due to their content of neurotoxins, as for example the red alga Digenea simplex which has been used for the treatment of roundworm disease for centuries, due to the content of kainic acid (KA) (Higa and Kuniyoshi 2000). Kainic acid is the only toxin reported as produced by macroalgae found in Europe. Mouritsen (2013) reviewed the content of kainic acid in dulce, excluding the markedly higher levels reported by Ramsey (1994), indicating that this work had methodological problems or epiphytes as source of Kainic acid. Algae containing both domoic acid and kainic acid have been used for medical purposes including treatment of roundworms (Holdt and Kraan 2011). High doses of kainic acid can cause neurotoxic effects, but such high doses are unlikely to be obtained from consumption of dulce (Mouritsen, Dawczynski et al. 2013).

Radioactivity There are few publications that describe food safety aspects of radionuclides in macroalgae. However, Fucus spp. are known to have a high uptake of the radionuclide Technetium-99 (Sjotun, Heldal et al. 2011), with increasing concentrations from young to older growth segments (Heldal and Sjotun 2010). Tuo et al (2016) found no higher levels of different radionuclides in different seaweed species compared to other seafood, vegetables or meat products. Similarly, Moreda-Piñeiro et al. (2011) concluded that radiation levels in typical Japanese and Korean foodstuff, which include seaweed, are safe and at the same level as other countries. In general, no levels of concern with respect to food safety has been found in seafood (pers. comm. J. Klungsøyr, Institute of Marine Research, Bergen, Norway).

Micro-organisms The surface of macroalgae represents important habitats for micro-organisms (Bolinches, Lemos et al. 1988; Jensen, Kauffman et al. 1996; Friedrich 2012) and like all eukaryotes, they harbour microbes in high numbers and of a rich diversity (Lachnit, Blumel et al. 2009; Lachnit, Meske et al. 2011; Bengtsson, Sjotun et al. 2012; Lachnit, Fischer et al. 2013; Hendriksen and S. 2014; Marzinelli, Campbell et al. 2015). In particular, the bacterial microbiota is ample. Bacterial numbers from 101 to 108/cm2 are reported, and the numbers seem to increase with higher water temperatures. The bacterial cell densities in the biofilms of healthy individuals varies between the different macroalgae species (Bengtsson, Sjotun et al. 2010; Wahl, Shahnaz et al. 2010). Furthermore, epiphytic communities on macroalgae may be similar in their composition, however could be different form the surrounding water communities (Bolinches, Lemos et al. 1988) indicating algae-microbe interactions.

Even though the nature of interactions between macroalgae and bacteria is very complex and poorly understood, these micro-organisms seem to play a role in the host health and infection defence (Matsuo, Imagawa et al. 2005; Fernandes, Case et al. 2011; Campbell, Verges et al. 2014). However, some bacteria may also be pathogenic to the algae itself.

The diversity of bacteria on the surface of macroalgae is dependent on a variety of biotic and abiotic factors, such as the algal species and physical characteristics, habitat and the bacterial load of the surrounding waters (Egan, Thomas et al. 2008; Egan, Harder et al. 2013). The microbiota occupying the surface of macroalgae may be indigenous to the marine or brackish water, or originate from terrestrial areas. Bacteria associated with macroalgae in unpolluted areas originate from the microbiota of the surrounding waters, and they grow and form biofilms on the surface of the algae. In waters with anthropogenic influence, including livestock associated activity, intestinal bacteria found in sewage or run of from land, may add to the macroalgae microbiota.

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Bacteria associated with macroalgae may be beneficial to the algae (Wahl 2008; Goecke, Labes et al. 2010), and thus live in a symbiotic relations (Egan, Harder et al. 2013), or are related to disease in and decomposition of dead algae (Largo, Fukami et al. 1995; Largo, Fukami et al. 1997; Largo, Fukami et al. 1999; Vairappan, Suzuki et al. 2001; Wang, Shuai et al. 2008). The algal bacterial pathogens associated with macroalgae are predominantly non-pathogenic to humans. Bacteria associated with macroalgae may produce toxins, signalling compounds, and secondary metabolites, however rather than posing a threat to human health, these may act as an interesting reservoir for novel bioactive compounds (Egan, Thomas et al. 2008).

Most studies concerning microbial communities associated with macroalgae have an ecologic focus, describing the numbers, diversity and role of bacteria on the surfaces of the algae (Bolinches, Lemos et al. 1988; Jensen, Kauffman et al. 1996; Egan, Thomas et al. 2008; Lachnit, Blumel et al. 2009; Bengtsson, Sjotun et al. 2010; Goecke, Labes et al. 2010; Olson and Kellogg 2010; Bengtsson, Sjotun et al. 2012; Friedrich 2012; Egan, Harder et al. 2013; Lachnit, Fischer et al. 2013; Martin, Barbeyron et al. 2015). There are however, considerably fewer publications dealing with human pathogenic bacteria associated with macroalgae, compared to those dealing with antagonistic activities of algae-derived substances against human bacterial pathogens. When combining the name of algae and pathogen in a literature search, exemplified by Laminaria digitata + «human pathogen», would give a reference related to antimicrobial activity against Mycobacterium tuberculosis (McDowell, Amsler et al. 2014). Searching for all the relevant macroalgae species + “Bacillus cereus”, all references found dealt with antibacterial activity against this pathogen.

A key issue is if macroalgae may act as reservoirs for faecal bacteria, including potential human pathogens, and if so do the microbe-algae association enhance the survival time of such bacteria in the marine environment. Faecal bacteria are commonly detected in near shore marine waters (Boehm 2007) and in organisms performing water filtration, such as bivalves (Lunestad, Frantzen et al. 2016).

Human pathogenic bacteria not originating from the sea may, occasionally be found on macroalgae. Theoretically, any pathogen derived from man or animal may find its way to the sea and contaminate the surface of any marine animal or plant, including algae. Several studies describe this phenomenon, but the risk associated with algae cannot be expected to be higher than what is found for other non-filtering organism. Moore et al. (2002) examined the surface microbiota of dried dulce (Palmaria palmata) collected from the coast of Northern Ireland, and detected no intestinal pathogens using conventional microbiological techniques. The authors included analysis for toxigenic E. coli, bacteria in the genii Campylobacter and Salmonella, as well as Staphylococcus aureus, Listeria monocytogenes and fungi.

Whitman et al. (2003) investigated the occurrences of E. coli and enterococci of Cladophora from Lake Michigan and abundant occurrences were found (up to 97 %), with mean log densities of 5.3 ± 4.8 and 4.8 ± 4.5 per gram dry weight. Both E. coli and enterococci survived for more than six months in sun-dried Cladophora mats stored at 4°C, and the remaining bacteria in the dried alga readily grew upon rehydration. As a follow-up, in experiments by Byappanahalli et al. (2003) it was shown that indicator bacteria like E. coli and enterococci can persist for extended periods and are even able to grow on the surface of Cladophora sp., particularly during warm summer months. These findings are from fresh water, however, and Cladophora is probably not used for food purposes.

The indigenous microbiota of brackish and marine water are, predominantly not considered to have a direct pathogenic potential in humans, with one important exception; some of the bacteria in the genus Vibrio. In contrast to most other bacteria of importance for seafood safety, members of this group have the marine and estuarine environment as the main natural habitat (Baumann, Furniss et al. 1984; West 1989; Sakata 1990). There is no documented correlation between the occurrence of vibrio and indicator bacteria of faecal origin, thus commonly applied indicator organisms as coliforms do not give information on presence of potentially pathogenic vibrio.

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The incidence and density of human pathogenic vibrio in the environment, and consequently in seafood products including macroalgae, are highly dependent on the ambient water temperatures. It is well documented that these bacteria are occurring in considerably higher numbers at increased water temperatures (West 1989; O'Neil, Jones et al. 1992; Høi, Larsen et al. 1998; Baffone, Pianetti et al. 2000; Oliver and Kaper 2001; Dalsgaard 2002; Adams and Moss 2008).

Bacteria in the genus Vibrio may be detected in seawater, bivalve mussels and marine sediments in Norway during the summer months (Gjerde and Bøe 1981; Ellingsen 2008). However, the isolates are neither of the pandemic types (O1, O139), nor carrying pathogenicity genes (tdh, trh). Typical summer

maximum seawater temperatures in Norway may wary from approximately 10C in northern parts to

25C in southern parts.

Several of the human pathogenic vibrios are described associated with macroalgae. From Japanese waters V. parahaemolyticus have been isolated from Ulva sp., Fucus sp., Laminaria sp., and Porphyra sp. (Mahmud, Neogi et al. 2007) and V. vulnificus were found on Porphyra sp., Undaria sp., Laminaria sp., and Fucus sp. (Mahmud, Neogi et al. 2008). In a study by Chan and McManus (1969), vibrios were found to be the predominant bacteria growing on Ascophyllum nodosum.

Even though domestically acquired food borne infections with vibrios have been observed sporadically in Norway, the registered numbers are very limited and no cases have been shown connected to consumption of macroalgae. Furthermore, bacteria in this genus are not considered robust, are relatively sensitive to heating, drying, and several other preservation techniques, as well as the low pH in the stomach of humans. Thus, it is not likely that vibrios will survive the production processes relevant for macroalgae for food and feed with the exception of algae used directly or after freezing.

Some environmental bacteria not having the aquatic habitat as its niche, may also pose a challenge for food safety without giving a direct risk of infection. Of highest importance are the spore formers Bacillus sp. and Clostridium sp., originating from soil by run of from land. As in other food and feed, members of these geni may produce toxins of health concern, if products are stored under improper time and temperature conditions. The risk for these agents for products from macroalgae are however largely unknown, and more work should be done to unravel the possible challenges posed by spore formers.

Many macro-algae are rich in bioactive compounds, which have antioxidant properties, and also have antimicrobial activities against food pathogenic microorganisms. Dussault et al. (2016) showed that macroalgal extract had antibacterial activity against Listeria monocytogenes, Bacillus cereus and Staphylococcus aureus. Meillisia et al. (2013) found that extracts of Saccharina (Laminaria) japonica showed antibacterial activity against Salmonella Typhimurium, Staphylococcus aureus and Bacillus cereus. Amiguet el al. (2011) found that glycolipid-rich extracts of Fucus evanescens in culture have antibacterial activity against Haemophilus influenzae, Legionella pneumophila, Propionibacterium acnes, Streptococcus pyogenes, Clostridium difficile and methicillin-resistant Staphylococcus aureus.

In an ongoing study, macroalgae harvested from Norwegian waters have been analysed for the presence of Listeria monocytogenes, pathogenic vibrios, enterococci, coliforms and thermotolerant coliforms, and none of these were detected in any of the samples (NIFES unpublished results).

Based on the studied literature, the question regarding the possible enhanced survival faecal bacteria and potential human pathogens associated to macroalgae remain largely unresolved.

Viruses rank among the most important infective agents causing food- and waterborne gastrointestinal disease worldwide (Cook and Richards 2013). In particular, norovirus cause large outbreaks in all age groups. For seafood organisms, the filter feeders are particularly prone to virus accumulation. As non-filter feeders, the macroalgae are not considered risk organisms for food or feed borne viral

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transmission. So far only a very limited number of outbreaks have been linked to macroalgae (Park, Jeong et al. 2015).

In conclusion, macroalgae are densely populated by bacteria on their surfaces. Some of these bacteria have a potential as human pathogens or could make challenges during processing and improper storage, but the importance of algae in feed or food borne disease cannot be expected higher than for other non-filtering marine organisms used for such purposes, including fish. Furthermore, the macroalgae are not considered risk organisms for food or feed borne viral transmission.

Microplastics Recently, interaction of microplastics with macroalgae have been addressed for the first time. In laboratory experiments, the seaweed Fucus vesiculosus retained suspended microplastics on its surface (Gutow, Eckerlebe et al. 2016). Any organism feeding on such algae might consume the plastic particles as well. This hypothesis was corroborated by studying the periwinkle Littorina littorea, which readily consumed such algae without preference for uncontaminated ones (Gutow, Eckerlebe et al. 2016). The potential entrance pathway for microplastics and associated contaminants from macroalgae to humans should be investigated. The possibility of bioaccumulation would be one aspect of such investigation. Retention levels of the plastic on the algae only reflected the concentration of the surrounding waters, but suspended particles do accumulate in macrophyte habitats (Gutow, Eckerlebe et al. 2016). Therefore, bioaccumulation might not occur within in the plant, but through the macroscopic properties of the habitat. Concerning the consequences for the macroalgae themselves, it can be speculated that, at high concentrations of microplastics pollution, their photosynthesis might be hampered, as it was shown for microalgae (Bhattacharya, Lin et al. 2010), with increasing effects at decreasing particle size (Sjollema, Redondo-Hasselerharm et al. 2016). This might affect the growth efficiency of the algae.

Digestibility of seaweed carbohydrates. While most land plants store carbohydrate as starch with high energy value, the marine algae is known to possess several other polysaccharides with lesser energy value when applied in food or feed.

In brown algae, including kelp of the Laminaria family, alginates are predominant. Alginates are polysaccharides consisting of long chains of mannuronic and guluronic acids. These are in literature mainly regarded as fibre with little or no energy content.

The most important red algae used for consumption in Norway is dulce (Palmaria palmata). Red alga polysaccharides mainly consist of carrageenans and agar. Data on nutrient content of dried Nori (macroalgae used in Japanese style dishes) varies considerably. In the Norwegian food composition table (www.matvaretabellen.no) it is stated to have 12% water and to contain 55 % carbohydrate in the form of starch, and no fibre. This data seems to need updating. The given protein content in the Norwegian vs. the Canadian food table is also very different, but here methodology might be an important issue.

Also Sea lettuce (Ulva lactuca), the only major green algae used for human consumption, is known for special content of its polysaccharides. This includes high level of the unusual sugar rhamnose, also found in pectin.

It is important to adjust the impression that the carbohydrates in marine algae gives energy in line with vegetables from terrestrial environments. On the other hand, from a human health point of view, an increased consumption of indigestible components as well as reduced energy intake might be

19

favourable. For macroalgae, this is particularly relevant as they may contain other essential compounds such as trace elements.

Frequent eating of seaweed alters gut microflora (Hehemann, Correc et al. 2010), and further studies on the possible effects on altered digestibility have to be conducted.

The present evaluation is based on the scarce data available. The occurrence data indicate that Norwegian algae may contain elevated levels of arsenic and cadmium, particularly in brown algae. The levels of arsenic and cadmium may limit the use of some macroalgae as feed and food ingredients. More occurrence data are needed to fully describe the occurrence of arsenic and the heavy metals in algae from Norwegian waters. New data sets should cover seasonal variation and different locations along the coastline.

The lipid content of macroalgae is low and the levels of persistent organic pollutants is in accordance with this also low and lower than comparable food items. There are, however, very few published data available in the field.

Levels of iodine in different types of macroalgae is high and only a small intake of dried macroalgae may exceed the recommendation of iodine intake. At the same time, more knowledge of the bioavailability needs to be considered as it is of importance that the iodine status is brought to the level that the population is euthyroid.

Some species of macroalgae produce toxins and other toxins are produced by epiphytes attached to the algae. No poisonings have been reported in Europe, and for the toxins that have been reported from a few European studies, the levels have been low and without any concern for human health. Some incidents of poisoning have been reported from Asia where epiphytic blue-green algae are the most probable source. Anti-nutrients such as polyphenols are present in macroalgae, giving negative effects on grazing snails and fish. However, no documentation of negative effects from algal consumption in humans could be found, while use of such substances in medicine is well described.

Macroalgae do accumulate radionuclides, but few studies focus on food safety and no levels of concern for food safety have been found.

Macroalgae are densely populated by bacteria on their surfaces. Some of these bacteria have a potential a human pathogens, or could make challenges during processing if improperly stored. However, the importance of algae in feed or food borne disease, including viral contagious agents, cannot be expected to be higher than for other non-filtering marine organisms used for such purposes, including fish.

Microplastics, defined as plastic particles smaller than five millimetres, are now common at all levels of the marine environment. Such particles are prone to accumulation of organic contaminants, and may subsequently adsorb onto macroalgae, potentially introducing the particles and their associated contaminants to animals and humans by food and feed.

Macroalgae contain polysaccharides that are rather different form land living food and feed plants, where starch is the major polysaccharide. The knowledge of the available energy content of these are low but in many cases they are more fibre than energy giving compounds. From a human health point of view, an increased consumption of indigestible components as well as reduced energy intake could be favourable. In feed perspective this could be a problem.

5. CONCLUSIONS

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The available information on the amount of macroalgae or products from macroalgae used in feed and as food in Europe, including Norway is sparse. As possible health impact on animals and humans is connected to exposure, more information on human consumption and feed applications are considered necessary.

The possible effect of processing on the bioavailability of components in macroalgae is largely unknown. However, for iodine food preparation and cooking methods will influence the final iodine content in the product, with an observed reduction of up to 70% after five minutes of boiling in water. One should keep in mind that the boiling water may be consumed by inclusion in e.g. soups, and the iodine lost from the macroalgae during boiling may be reintroduced.

After reviewing the literature on possible risks associated with macroalgae as food and feed, it became obvious that there is a substantial lack of data on most factors of relevance. More work to examine the prevalence and importance of chemical and biological risk factors should be considered. For further risk evaluation of food safety associated with macroalgal consumption, information on bio availability will be necessary. The structural polysaccharides of macroalgae have low digestibility and may bind certain heavy metals. More absorption studies including iodine, cadmium and inorganic arsenic from macroalgal matrices should be performed in order to provide such information. To challenge the assumption that there is a low risk of finding pathogenic bacteria on macroalgae, microbial studies of macroalgae compared with molluscs from contaminated waters should be performed.

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Amiguet, V. T., L. E. Jewell, et al. (2011). "Antibacterial properties of a glycolipid-rich extract and

active principle from Nunavik collections of the macroalgae Fucus evanescens C. Agardh

(Fucaceae)." Canadian Journal of Microbiology 57(9): 745-749.

Baffone, W., A. Pianetti, et al. (2000). "Occurrence and expression of virulence-related properties of

Vibrio species isolated from widely consumed seafood products." International Journal of

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Baumann, P., A. L. Furniss, et al. (1984). Facultatively anaerobic Gram-negative rods. Genus I Vibrio

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Bengtsson, M. M., K. Sjotun, et al. (2012). "Bacterial diversity in relation to secondary production and

succession on surfaces of the kelp Laminaria hyperborea." Isme Journal 6(12): 2188-2198.

Bengtsson, M. M., K. Sjotun, et al. (2010). "Seasonal dynamics of bacterial biofilms on the kelp

Laminaria hyperborea." Aquatic Microbial Ecology 60(1): 71-83.

Bhattacharya, P., S. J. Lin, et al. (2010). "Physical Adsorption of Charged Plastic Nanoparticles

Affects Algal Photosynthesis." Journal of Physical Chemistry C 114(39): 16556-16561.

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variability." Environmental Science & Technology 41(24): 8227-8232.

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communities associated with Fucus vesiculosus and Ulva rigida in an estuary." Microbial

ecology 15(3): 345-357.

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205-216.

6. LITERATURE LIST

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Byappanahalli, M. N., D. A. Shively, et al. (2003). "Growth and survival of Escherichia coli and

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