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Subterranean aquatic ecology of the Vale of Glamorgannew results from a recent groundwater survey

Gareth Farr, Environment Agency Wales February 2012gareth.farr@environment-agency.gov.ukMirconiphargus Image : Ken Clarke FBA

In today's talk I hope to give a short overview of hypogeancrustaceans (Stygobites) that are found in Wales and the VOG.

I will discuss the range of locations that they inhabit within the groundwater system and the methods we use to collect specimens.

Three of the recorded species are new to the VOG and one represents the first record from Wales.

I will also talk about future work and raising the profile of the groundwater ecosystem.

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From L.Maurice. 2009. Groundwater Ecology Literature Review

In blue are stygofauna in UK, in red circles are stygobites covered in this presentation

The stygobites we will talk about today are all crustaceans

We will look at the amphipods and isopods

However oligochetes, ostracodes and copepods do turn up in the groundwater samples but are not discussed in this talk.

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Groundwater as an ecosystem

Stygobites like all living things need space to move in and a source of food and oxygen.They mainly inhabit karstic aquifers such as limestone or chalk. However they are also found in other fractured aquifers and unconsolidated deposits, such as the hyporheic zone of rivers.

Karst and fractured aquifers allow the rapid movement of organicmaterial (a possible food source) to enter the groundwater and rapidly travel to great depths.

However we only have access to small parts of many aquifers via boreholes, wells, springs and caves. Many of the smaller fractures and fissures are simply inaccessible.

Microcavernous <1mmMeascavernous 1 – 200mmMacrocavernous >200mm

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All records in Wales - 2012

5 species

220 individual specimens at

53 sites

Devensian Glacial Limit

Recording in Wales is perhaps the lowest in the UK

Historically many records are from the Limestone caves of South Wales. This reflects accessibility to humans as much as it reflects where stygobitic animals inhabit.

The Devensian Glacial Limit was thought to be a controlling factor on the distribution of stygofauna. The ice sheets may well have made many places inhospitable, turning ground into frozen tundra and stopping the flow of organic matter into the groundwater.

It is however clear that stygofauna exist above the Devensian limit, and may have existed in refugea ?sp during the ice age.

The low diversity of UK stygofauna compared to the continent may well be caused by the last glaciation.

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Sampling at a monitoring borehole

Boreholes provide access to the groundwater system and aquifers.

The diagram shows how water and organic material may travel through the limestone aquifer, in this case from a loosing stream (such as the River Alun near Ogmore).

Boreholes may act almost as sumps with unwitting stygobites being washed into the borehole. On the plus side organic matter also accumulates here providing a food source.

Many of the boreholes are ‘open holed’ I.e they have no lining and fractures in the bare rock are directly connected.

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Sampling at a monitoring borehole

The image to the left is an Environment. Agency monitoring borehole.

The nets on the right, manufactured by GB Nets are specially made to sample boreholes.

They are 250 microns and are weighted at the base, to allow the net to fall to the base of the borehole.

The weight is also used to disturb the sediment at the base of the borehole.

The net is then rapidly pulled up - sometimes on 100m or more of cable.

This is repeated three times.

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Sampling at a shallow well

Shallow wells (often covered) also provide a habitat for stygobites washied in from the underlying aquifer.

Wells offer quite a different habitat than boreholes.

Wells will also have a host of surface water creatures and plants. This may provide more food sources, but also more competition.

Wells are sampled using a long handled pole with a net attached.Again you can chose your mesh size but the finer the better to catch the really small animals.

A general sweeping motion is used, and if possible some of the sediment at the base of the well is disturbed.

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Sampling at a shallow well

This is a historic covered well. It takes water from the Carboniferous Limestone aquifer.

Stygobites and surface water animals both exist hand in hand.

The sampling method involved a long handled pole with the borehole net simply tied in place and swept around for a few minutes.

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Sampling in the hyporehic zone

The Hyporehic Zone

The base of many rivers are suitable for stygobites.

The unconsolidated gravel allows movement.

Groundwater feed from underlying aquifers may provide a way to move from bedrock to hyporehic zones.

A Bou-Rouch pump is used to sample this zone.

The pump is driven into the base of the river using a sledge hammer.

The pump is operated and water and sediment collected in a fine mesh bag.

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Sampling in the hyporehic zone

A Bour Roch pump in action (Lee Knight).

This is actually a spring which forms a small tributary to a main river.

Areas of rivers where groundwater is known to be upwelling are targeted.

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Sampling at a spring outflow

Stygobites will be washed out of aquifers.

This occurs where groundwater flows out of the system, I.e springs.

This spring flwos into a river near the coast. During high tides the water can become saline.

There were no stygobites found at this location. Although plenty of Gammerus and Asellus, much larger freshwater animals.

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Sampling at a large spring outflow

Apologies for the poor quality picture, taken on my phone !

Another spring but this time much larger and without the influence of saline waters.

The drift net is deployed for several days.

It has a fine 250 micron mesh and will trap all animals that arewashed out of the cave system.

This is an effective method of sampling at large springs as it allows deployment over several days.

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Records Prior to survey

There are only four historical records

Only 2 Species are represented over records from 1957 - 2009

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Records post survey

The recent survey was concentrated around the Ogmore area.

There are several large springs and Env. Agency monitoring boreholes allowing sampling access.

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Proasellus cavaticus – Only five records in 50 years commonly recorded from cave systems in WalesImage Lee Knight / Chris Proctor

Common in the caves of south Wales.

This is first records from VOG for almost 50 years.

Although it is not thought this is rare in VOG just not recorded

http://www.freshwaterlife.org/hcrs/species.html.

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Crangonyx subterraneus – First record for VOG ? Only third record in Wales Image Chris Proctor

Only a few specimins in Wales

Has turned up in shallow wells in Portcawl living with surface animals

http://www.freshwaterlife.org/hcrs/species.html

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QuickTime™ and a decompressor

are needed to see this picture.

Niphargus fontanus – only one record in this surveyImage Phil Chapman

Most common in old samples ? 1957 and 1971

Only 1 record in recent survey

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Microniphargus leruthi – First record in WalesImage Lee Knight / Chris Proctor

First recorded in 1934 in Europe

2006 in County Courk Ireland

2010 Swildons Hole Mendips

2011 Vale of Glamorgan - First Welsh Record

Often overlooked as a juvenile Niphargus

Only 2mm or less in size

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Three new species and seven new sample locations in the VOG

201127Microniphargus leruthi

2011328Crangonyx subterraneus

201111Niphargus fontanus

no records since 1971 Niphargus aquilex

2011753Proasellus cavaticusdateslocationsabundancespecies

Post 2011

1957 - 1971322Niphargus aquilex

1960-200925Proasellus cavaticusdateslocationsabundancespecies

Pre 2011

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All records Vale of Glamorgan (top) all of Wales (below) Proasellus cavaticus seams to be the most dominant species

Proasellus cavaticus

Niphargus aquilex

Niphargus fontanus

CrangonyxsubterraneusMicroniphargus leruthi

Proasellus cavaticus

Niphargus aquilex

Niphargus fontanus

Crangonyxsubterraneus

Microniphargus leruthi

Dominance of Proasellus in Wales and VOG is interesting.

May reflect sampling technique, large number of animals etc etc ?

Perhaps not really enough data to make any large assumptions

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Water Quality

6.210.864.49Dissolved Oxygen mg/l

55.174.241.3Dissolved Oxygen %

530900330Conductivity @ 25us/cm

7.37.976.79pH

12.26157.6Temperature oC

AverageMaximumMinimum

Groundwater often has relatively stable physiochemical conditions

Water Quality for Schwyll and also sites near Porthcawl.

Temperature – a little high on average may reflect sampling procedure

pH – nothing exciting

Dissolved oxygen – again nothing exciting

The Porthcawl sites (St Davids Well and Ffynnon Fawr) are what have given the higher EC readings other that that the EC is actually quite stable

Main WQ conclusion is that Groundwater is quite a stable environment

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Water Quality

Nitrates are not elevated, dominant ions are calcium and bicarbonate

250410218Bicarbonate HC03 mg/l

7714643Calcium Ca mg/l

0.0250.0370.02Phosphate mg/l P

3.38.511.12Nitrate mg/l as N

AverageMaximumMinimum

Organic compounds are limited, there is no major organic pollution

Water Quality for Schwyll and also sites near Porthcawl.

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Results

Microniphargus leruthi First record in WalesCrangonyx subterraneus First record in VOGNiphargus fontanus First record in VOG

Water quality is good with low nutrients levelsThere is no extensive organic pollutionThere are no over abstraction issues

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Continue collection

Limestone areas, Pembs, North Wales and Anglesey

Raise profile of groundwater as an ecosystem

New species may yet to be found ???

Future work

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acknowledgments and thank you

•Lee Knight (National Recorder)•Caleb Lambourne (Environment Agency Wales)•Julian Carter (NMGW)•Images Ken Clarke (FBA) & Chris Proctor •also Tim Johns and Lou Maurice

Mirconiphargus Image : Ken Clarke FBA

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Hypogean Crustacean Recording Schemehttp://www.freshwaterlife.org/hcrs

Review of the subterranean aquatic ecology of England and Wales, 2008.http://publications.environment-agency.gov.uk/PDF/SCHO0408BNYC-E-E.pdf

Groundwater Ecology Literature Review 2009 http://nora.nerc.ac.uk/14751/

British Geological Surveyhttp://www.bgs.ac.uk/research/groundwater/ecology/home.html

Further Reading

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