Benthic indicators

Dr. Ángel Borja

aborja@pas.azti.es

Fundación AZTI

Marine Research Division

Oban (Scotland)

January 2006

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Selected benthic indicators(proposed)

1- Name of indicator, authors i. Existence of macrofauna in sediment (UGOT)

ii. 2- Computation : Formulae, or model output.

i. To maintain a macrofauna at the sea bed below a net pen there is a maximum acceptable flux of organic matter (F2max) from the farm to the bottom determined from

ii. min22max2 OO

UF i

bent

iii. where Ubent is the horizontal current velocity just above the turbulent benthic boundary layer, so that β Ubent is the effective velocity transferring oxygen to the bottom (β ~ 2·10-3), α is the fraction of the particulate organic matter from the farm that oxidises within the farm area, η is the amount of oxygen necessary to oxidise 1 g of carbon to carbon dioxide and water (~3.5 gO2/gC), O2i is the concentration of oxygen just above the turbulent benthic boundary layer and O2min the minimum oxygen level to sustain benthic infauna.

iv. v. The actual sedimentation rate F2 can be measured with sediment traps beneath a farm

or calculated from MOM-system dispersion model. vi.

1- Name of indicator, authors AMBI Borja, Á.; Franco, J.; Pérez, V. (2000). A Marine Biotic Index to Establish the Ecological Quality of Soft-Bottom Benthos Within European Estuarine and Coastal Environments. Marine Pollution Bulletin, 12 (4): 1100-1114. 2- Computation : Formulae, or model output. AMBI = ((0 x %GI) + (1.5 x %GII) + (3 x %GIII) + (4.5 x %GIV) + (6 x %GV))/100 The result is a number in a range of 0-6 (7 for azoic sediments) that can be simplified into five classes from undisturbed communities to extremely disturbed communities (sensu Grall and Glémarec (1997)), or from High to Bad Status (sensu European Water Framework Directive (WFD), in the assessment of the Ecological Status). There is a freeware tool at www.azti.es to calculate the AMBI automatically and visualize graphically the results. It exists a guideline in using AMBI (Borja and Muxika, 2005)

1 Name of indicator, authors Impact of shellfish culture on trophic groups of the benthic macrofauna 2 Computation : Formulae, or model output. Change in trophic groups: Before/after beginning of aquaculture operation Filter-feeders Deposit feeders carnivores ratio filter-feeders/surface deposit feeders

1 Name of indicator, authors Macrobenthic biomass fractionation index (BFI)

2 Computation : Formulae, or model output. (Macrofaunal Biomass retained on 0.5mm sieve olny / Macrofaunal Biomass retained on 1.0mm+ 0.5mm sieve) 8*100 Macrofauna is sieved sequentially over 1mm and 0.5 mm sieves. The large body-size fraction is retained on 1mm sieve whereas the small body-size fraction (containing the opportunistic species) passes through 1mm and is retained on 0.5mm sieve. The index takes values from 0-100%

1 Name of indicator, author

SHANNON-WIENER INDEX for evaluation of MEIOFAUNAL HARPACTICOID COPEPOD DIVERSITY (mostly second meiofaunal dominant) and SEDIMENT TEST Borut Vriser, Mateja Grego, NIB 2 Computation : Formulae, or model output.

Where pi is the proportion of a particular species in a sample which is multiplied by the natural logarithm of itself. For sediment test, we take corer samples from beneath the mariculture (A), and other samples from different controll points (B). Later compare samples from A and B. Comparison betwen affected and unaffected (natural) environment.

ii

s

InppH

1 Name of indicator, authors SEDIMENT TEST, MEIOFAUNA Mateja Grego, Borut Vriser, NIB

2 Computation : Formulae, or model output. We take 2 paralel box-corer samples from the local area both from the position Nº1. One box we situate at the control site-C- and the second box-M- under mariculture. After a certain time we collect boxes and analyse the subsamples. Compare samples from M and C. This test should be performed 6-9 times.

1 Name of indicator, authors Infaunal Trophic Index (ITI) Not widely accepted as an indicator of impact but may merit further testing. Used partly in Scottish regulatory monitoring surveys and modelling and tested in North American waters. Word (1979); Mearns and Word (1982) (From SAMS) 2 Computation: Formulae, or model output. ITI (range 0-100) has been tested to some extent for assessing the impact of aquaculture:

N + N + N + N

N3 + N2 + N1 + N0( 33.3 - 100 = ITI

4321

4321

where Ni is abundance of organisms in trophic group i. See text below for explanation.

1 Name of indicator, authors Univariate descriptions of macrofauna community (with some indices also applicable to meiofauna) S (number of species), A (Abundance), Biomass (B) Also B/A, A/S, Shannon-Wiener H’ (diversity), Pielou’s (Evenness), Simpson, top 5 most abundant species Indicators species and families, ratio of biomass retained on 0.5 mm sieve to 1.0 mm sieve (Karakassis and Lampadariou, unpublished) Various authors for other indices (From Sams)

2 Computation: Formulae, or model output. S, A and B, S/A, B/A are calculated from taxonomic identification species lists. H’, Evenness and Simpson can then be subsequently derived. Formulae for these are given in standard benthic ecology text books (e.g. Levinton, 1982), or are calculated by statistical packages, eg. PRIMER. Certain indicator species and families have been shown to indicate impact by their presence/absence (recent example in the Mediterranean - Karakassis and Lampadariou, unpublished) Classic trends of each of indices (S, A, B) are documented in the literature and the range of these indices are site and environment specific. Therefore, it is not appropriate to specify a range for these indices.

1 Name of indicator, authors Multivariate ordering of macro- and meiofaunal community Not an accepted or widely published method (as yet). For general discussion and background of the technique, see Greenacre, M.J., 1984. Theory and Applications of Correspondence Analysis, London, 364

pp. Jongman, R.H.G., ter Braak, C.J.F. and van Togeren, O.F.R., 1987. Data analysis in community and landscape ecology. Pudoc, Wageningen, 299 pp. For actually running the technique, and some explanation of the mathmatical basis, see ter Braak, C.J.F. & Smilauer, P., 1998. CANOCO Reference Manual And User Guide To CANOCO For Windows. Software for Canonocal Community Ordination (version 4). Centre for Biometry, Wageningen, 351 pp. (From SAMS) 2 Computation: Formulae, or model output. The fraction of the variance of a particular species in the canonical correspondence analysis is calculated, and the cumulative percent variance (cumulative fit per species as a fraction of variance of species) is tabulated. The species can then be ordered, and the top contributors assessed.

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Selected benthic indicators(criteria)

The criteria for selection were:• Direct relevance to objectives.• Clarity in design: clearly defined, avoiding confusion in their

development or interpretation. • Realistic collection or development costs: must be practical. • High quality and reliability: the information they provide should be as

good as the data from which they are derived. • Appropriate spatial and temporal scale. • Obvious significance: should easily be understood by stakeholders.

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Selected benthic indicators

1. Existence of macrofauna• It is a good example of an index ideal for the ECASA tool pack as it

combines physics, biology and biochemical factors. It is easy to understand and has potential. This indicator focuses on measuring variables (e.g. OM flux) that exert "pressures" which affect the macrobenthic community, rather than quantifying the macrobenthos itself.

• However, it is not clear how the macrobenthos presence/absence data are used in the UGOT MOM model. It is not clear that this indicator distinguishes between different types of macrofauna and could lead to erroneous conclusions on the basis of simplistic presence/absence criteria.

• More information is needed from the proposers of this index on a suitable method for measuring a representative benthic boundary layer oxygen concentration for use this index

2. AMBI• This index is well thought out, the software is easy to use and has

been widely tested in many different situations (good results with clear pollution gradients in farms from Spain, Italy and Greece). It is easily explained to stakeholders and makes use of quantitative benthic sampling. This is a promising approach which relies heavily on detailed characterization and understanding of local benthic community health. It is worthwhile testing as an indicator/model, but may not work in those sites where the sensitivity of local macrofauna to pollution is not known.

• AMBI requires more testing with North Atlantic data sets and for fish farm sediments and we believe this can be done through WP5. Their reliability/quality and for temporal/spatial scales can be improved with further testing of the index with fish farm data sets.

3. Trophic groups• The index is simple and can easily be explained to stakeholders. • It is not clear how this indicator is linked to macrobenthos. • If the index is the ratio of filter feeders to surface deposit feeders,

then this would result in a range of validity of 100% for “No impact”. This is the opposite to that specified in the document and so needs clarification.

• Some more information should be provided by the proposers on what method would be used to sample the filter feeders/deposit feeders. What level of taxonomic identification and skill is necessary to evaluate this index?

• Some of the subgroup members opine that sometimes it is difficult to assess.

4. BFI • This index is likely to be useful, easy to explain to stakeholders and

robust. As it is so simple and does not require identification skills it is also cheap. It should be tested in WP5 and perhaps beforehand, by the various PI's at the study sites. Although it seems promising, it is possible that the 0.5/1.0 mm seize size ratios may need to be modified at non-eastern Mediterranean sites, where ecologically significant macrobenthos body sizes may be approportioned differently. Some of the subgroup members do not found clear differences between the two fractions.

• Given the biomass of smaller organisms form the basis of this index, how sensitive is it likely to be to seasonal changes, equipment used and sample size and can this be tested in WP5?

5. Meiofauna (Univariates)• This indicator may be informative for environmental impact, but it

requires considerable local taxonomic expertise, is very time-consuming (i.e. expensive) and thus of dubious suitability for our purposes.

• Measuring meiofauna in addition to macrofauna provides useful information for assessing impact due to their shortened generation times and lack of planktonic phase. However, it is marked down in terms of realistic collection/development costs due to the additional expertise required for taxonomic identification of meiofauna.

• Some subgroup members commented that the meiofauna studies did not show the expected results. They found that the meiofauna distribution is too patchiness, big differences also in few centimetres in presence of morphological irregularity of sea bottom. This comment is valid for next indicator.

6. Meiofauna/sediment• This requires better explanation by the proposers. It is very

interesting and potentially of merit, but suffers somewhat in the design. The a priori assumption of uniformity between treatments may not be justified due to patchiness, and renders following statistical analysis problematic.

• A more appropriate technique for such an in situ ecotox approach may be using quantified cultures of meio/macrofaunal organisms that are delivered to study/control sites; in this way real changes in known sample populations can be assessed.

• This method is potentially extremely useful in directly targeting effects, but may suffer from costs/difficulties of culture and emplacement of cultures, but the potential benefits are large.

7. ITI• It is easily explained to stakeholders. It is not widely accepted due to some

debate on the trophic feeding groups that species occupy, but we think this only makes a marginal difference to the value of the index when compared with the variability between grabs. It has not been tested in many different environments and so we marked it down for quality and spatial/temporal scales.

• ITI correlates with other indices, modelled flux and it forms an important component of the DEPOMOD benthic module. It should continue to be tested alongside other indices such as AMBI, given that identification to species level will be undertaken as a matter of course to calculate univariate statistics.

• Limitations of ITI exist with low species numbers (e.g. less than 5), but this is common to most indices at low species numbers.

• This method requires good working knowledge of the taxonomy and trophic ecology of the local macrobenthos.

8. Macrofauna (Univariates)• This is a well established technique, unambiguous and

therefore scored highly. Stakeholders usually prefer one number to describe a community than several but it is our view that univariate statistics should always be specified alongside other indices.

• This approach employs a battery of the standard index calculations applied to the macrofauna community data. It is always worthwhile to do these calculations since they are easily executed once the macrobenthos community data have been obtained.

9. Multivariate analyses• We think it merits further testing for macro and meiofauna and have

some experience of using these analyses for assessing fish farm impact. However, we could not find much information in the published literature for fish farm sediments. Its design is not easily explained to stakeholders so we marked it down on a number of aspects.

• Just as the univariate indices are a good idea to tabulate, it is worthwhile doing the canonical correspondence analysis to see what this yields, especially since one of the PI's already has the software.

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Selected benthic indicators(evaluation)

CRITERIA

Exi

st. m

acro

faun

a

AM

BI

Tro

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BFI

(bi

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Mei

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univ

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Mei

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ITI

(inf

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Uni

vari

ate

Mul

tivar

iate

Direct relevance to objectives 5 5 5 5 5 5 3 5 5 Clarity in design 5 4 3 4 5 5 3 5 5 Realistic collection or development costs 5 5 3 5 4 4 3 4 4 High quality and reliability 5 5 4 5 5 5 3 5 5 Appropriate spatial and temporal scale 5 5 5 5 4 4 4 5 5 Obvious significance 5 5 4 5 5 5 4 4 4 TOTAL 30 29 24 29 28 28 20 28 28

Evaluator E

xist

. mac

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una

AM

BI

Tro

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ups

BF

I (b

iom

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frac

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inde

x)

Mei

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univ

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Mei

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ITI

(inf

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Uni

vari

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Mul

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Each proposer 30 29 24 29 28 28 20 28 28 SAMS 23 23 21 28 24 20 23 26 20 AZTI 22 29 19 24 21 17 23 28 21 MEAN 25 27 21.3 27 24.3 21.7 22 27.3 23

12 23 4 5678

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Conclusion

Although the indicator list has been scored and ordered from the most to the less suitable, we did not reject any of the indicators and think that most of these indicators could be tested by all partners in each of their respective sites, particularly the ones which are calculations based on species lists. BFI Indicator (and potentially Trophic Groups indicator) may well be rapid assessment tools, being considerably cheaper than full taxonomic identification. Existing Macrofauna Indicator is slightly different to the other indicators proposed as presumably it is useful for planning and monitoring. Only indicators involving meiofauna can produce problems in a general application due to the absence of experts.

Macrobenthos AZTI’s protocol

Dr. Ángel Borja

aborja@pas.azti.es

Fundación AZTI

Marine Research Division

Oban (Scotland)

January 2006

© AZTI-Tecnalia

Grab sampling

• Box corer (0.06 m2)• Van Veen (0.07 m2)• Both stainless steel• 3 replicates (benthos) +

1 sediment• Penetration at least 5

cm (depending on sediment)

• 1 mm mesh size sieve

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Sediment analysis

• Grain size (φ-scale: silt/clay fraction < 63 µm, 125 µm, 250 µm, 500 µm, 1000 µm, 2000 µm).

• We combine the Beckman-Coulter LS 13320 (laser diffraction) with aquatic suspension processing module (resolution 0.04-2,000 µm) (for small particle size) and sieving column (0.5 phi resolution) for higher grain size.

• Weight loss on ignition (450 ºC, 24 h); • In situ redox potential: a ORION

977800 platinum electrode, connected to a digital pH-meter/milivoltimeter CRISON 501 (resolution ± 1 mV).

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Macrobenthos samples

• Fixation: in a buffered 4% formaldehyde solution (1 part 40 % formaldehyde solution and 9 parts sea water). For buffering, sodium tetraborate (= Borax) in excess is used.

• Normally we use 1 l flasks• Staining: samples are sometimes

stained with Rose Bengal.• Sorting: magnification lamp and

stereomicroscope.• Biomass Determination: dry weight

(60ºC until constant weight, at least 24-48 h). Sometimes we determine also AFDW (500ºC, 6h).

Proposed Spanish Site

Dr. Ángel Borja

aborja@pas.azti.es

Fundación AZTI

Marine Research Division

Oban (Scotland)

January 2006

© AZTI-Tecnalia

Study Site

• San Pedro del Pinatar (Murcia) • Sea bass and sea bream (2000t) and

tuna (800t)• 5 farms• Previous data:

– Currents (DCM12), waves, etc.– CTD data– Modelisation– Surveillance (we need to obtain those

data)

695000 700000 705000 7100004175000

4180000

4185000

4190000

4195000

0 km 2 km 4 km 6 km

ADL

Viverátun

Blue&Green

Viveros Marinos Alba & Hermanos

Piscifactorías de Levante

SPAIN

FRANCE

30 m50 m

30 m50 m