Temporal trends in benthic infauna, epifauna and toxic microalgae

1. Temporal trends in benthic infauna, epifauna and toxic microalgae James Strong Queen’s University of Belfast Department of Agriculture and Rural Development NI

2. Overview Phytoplankton: Ongoing DARDNI monitoring of water and shellfish. Epifauna: Annual towed camera sledge surveys Infauna: Annual grab sample survey Deep sediment records: Coring undertaken by SLECI project

3. Strangford Lough Infauna • Why sample infauna? • Several studies have demonstrated that benthic infauna respond predictably to various types of natural and man-made stress (Smith 1997). • Infaunal assemblages are useful indicators because they have limited mobility and cannot avoid adverse conditions. • Benthic organisms have a wide range of physiological tolerances, feeding modes, and trophic interactions, making them sensitive to a wide array of environmental stressors (Smith 1997). • For these reasons, infaunal assemblages have been sampled annually in Strangford Lough since 1993.

4. Methods • Samples taken with a short-armed van Veen grab or Day grab in accordance with NMMP Green book guidelines. Sampling was undertaken in the same season each year. • Fauna separated on a 1 mm sieve and stored in 4% Formalin. • Sediment sub-sample taken from within the fauna grab and sized with laser granulometry. • Sampling stations: Green Island Passage (green dot), Trawl Zone (red dot) and Bird Island Passage (blue dot).

5. Methods Data analysis used PRIMER (Plymouth Routines in Marine Ecological Research), ITI (Infaunal trophic index) and AMBIO indices.

6. Statistics Example of species matrix Multivariate tests use all of the information in the species matrix Univariate measures have to reduce a samples’ content to one value

7. Results: ANOSIM Significant differences between years at three sites in Strangford Lough, as identified by ANOSIM (PRIMER). * One way analysis ** Crossed two-way analysis. 1993N = 1993 November (Winter) sampling

8. Results: Species richness Species richness per grab for three locations in Strangford Lough (1993-2002). Error bars are 95% confidence limits.

9. Results: Total number of individuals Total number of individuals per grab taken at three locations in Strangford Lough (1993-2002). Error bars are 95% confidence limits.

10. Results: Taxonomic diversity / ITI Taxonomic diversity with 95% confidence limits. Average ITI code with 95% confidence limits.

11. Results: AMBIO index (Borja et al. 2000) AMBIO coefficients for infaunal samples from three locations in Strangford Lough. Error bars are 95% confidence limits.

12. Results: W statistic W Statistic Two-way analysis (no replication): Sites: df=2, p= 0.51, Years: df = 6, p = 0.05. W (Warwick) statistic for the combined ABC graphs all three sites for each year. The value for 2000 is based on data from Green Island only.

13. Results: SIMPER • Pholoe sp. (scale worm) and Abra alba (bivalve) increased substantially in abundance (an order of magnitude) from 1993 to a peak in 1999/2000. • A pronounced ‘mast year’ of Myodocopida (ostracod) occurred in 2001 at Green Is. And Bird Is. • Notomastus sp. (bristleworm) and Aphelochaete marioni (bristleworm) also increased in abundance in the late 1990s. • Nucula nucleus (bivalve), Sphaerodoridae (bristleworm) and Modiolarca tumida (bivalve) approximately doubled in abundance before 2000 and declined steeply afterwards.

14. Results: BIO-ENV Spearman rank correlation between physical and biological data

15. Discussion • A crossed ANOSIM analysis determined that the infaunal communities were significantly different for all years, except 1993-1994 and occasionally 1993/94-1997: this was apparent at the three locations. • From 1997 to 2001, the average animal abundance increased by a factor of 6 at Green Island (max. 2001), and by 8 at Bird Island (max. 1999). Most of these changes were driven by ‘mast years’ of Pholoe sp. and Abra alba. • Total number of species per grab also increased during this period, although this was probably a result of differing ‘taxonomic effort’ by identifying researchers.

16. Discussion • There was no significant difference in the ITI or AMBIO coefficients between the sites or over time. • The overall tendancy for the W statistic to decline at the three sites suggests a steady series of species substitutions that changed the predominantly K-selected assemblages in 1993 to communities with a much greater proportion of r-selected species in 2001. • Changes in sediment particle size were not responsible for the changes in the infaunal communities.

17. Towed video analysis of Strangford Lough epifauna There are several attributes of the epibenthos that make this group an important target in environmental monitoring: • On rocky or tide-swept grounds, they may be the only significant component of the benthos. • Fish prey upon many epibenthic species. • These communities are sources of substantial primary production in shallower areas. • On softer ground, an epibenthic community can profoundly modify the physical environment. • Epifaunal surveys complement the information obtained from infaunal investigations.

18. Methods • Epibenthic video/stills sledge. • Between 3-5 tow tracks per year at Bird Island (blue), central trawl zone (red) and Green Island passage (green). • Epifauna cover assessed with the visual fast count method (details in Magorrian and Service 1998): ~ 3-4 counts per tow. • Separate starfish counts undertaken. • Semi-quantitative Modiolus clumping and epifauna evaluation • Visual fast count data analyzed with PRIMER.

19. Methods Modiolus reef structure and epifauna index

20. Results: Green Island passage Significant differences between years: one-way ANOSIM NA = not analyzed SIMPER analysis for Green Island

21. Results: Central Trawl Zone Significant differences between years: one-way ANOSIM SIMPER analysis for central trawl zone

22. Results: Bird Island passage Significant differences between years: one-way ANOSIM SIMPER analysis for Bird Island passage

23. Results: Starfish counts Starfish abundance for Green Island passage and the trawl zone between 1993 – 2002.

24. Results: Modiolus clumping and epifauna Clumping index for beds of Modiolus modiolus in Green Island passage and the trawl zone Epifauna index for beds of Modiolus modiolus in Green Island passage and the trawl zone

25. Discussion • At Green Island, no significant difference was detected between years and Modiolus remained abundant from 1993 to 2002. • Within the Central dissimilarity was greatest in 2002 - this was mostly due to the decline of M. modiolus and increase of Ascidiella aspersa. • Only recent surveys were available for Bird Island passage: 2001 was seen to be significantly different to previous years.

26. Discussion In conclusion, there are four striking features in the results: • Apparent decline of the population of Modiolus from the trawl zone in 2002. • The success of the population of Ascidiella aspersa in recent years. • The degraded condition of beds of Modiolus in 1999/2000 in Green Island passage and the trawl zone. • A large increase in the abundance of starfish in Green Island passage and in trawl zone.

27. Toxin producing and nuisance microalgae in Strangford Lough: An overview from 1996 to 2003 Queen’s University of Belfast Department of Agriculture and Rural Development NI

28. Introduction An algal bloom is essentially a rapid population increase, indicating ideal growing conditions and nutrients concentrations. Generally, these are naturally occurring, although there is an apparent increase in their frequency of blooms with human activities. Although many marine algal blooms cause water discolouration and are harmless, some species can produce toxins harmful to both humans and marine life. Shellfish for human consumption are monitored for toxins under the requirements of the EC Shellfish Hygiene Directive: both water samples and shellfish flesh are collected by the Food Standards Agency. Samples are subsequently delivered DARDNI of analysis.

29. Methods Four sites, namely Marlfield Bay (yellow), Paddy’s Point (red), Reagh Bay (blue) and Skate Rock (green), have been consistently sampled from 1996 to 2003. One litre water samples were taken as close to high tide as possible at each site and preserved with acidified Lugol’s iodine solution. A 50 ml subsample was taken from each sample. This was allowed to settle overnight before being examined using an inverted microscope.

30. Monitored microalgae in Strangford Lough, Northern Ireland

31. Results Cell concentration of Dinophysis norvegica at four sites in Strangford Lough (1996-2003).

32. Results Cell concentration of Dictyocha speculum at four sites in Strangford Lough (1996-2003).

33. Results Cell concentration of Gymnodinium spp. at four sites in Strangford Lough (1996-2003).

34. Results Cell concentration of Pseudo-nitzchia spp. at four sites in Strangford Lough (1996-2003).

35. Results Cell concentration of Phaeocystis sp. at four sites in Strangford Lough (1996-2003).

36. Discussion Five noteworthy bloom species: • July 1996, 1100 cells L-1 of Dinophysis norvegica. • 1997 and 2003, 1000-1500 cells L-1 of Dictyocha speculum • May 2000, over 8500 cells L-1 of Gymnodinium spp. at Paddy’s Point and over 2000 cells L-1 at Reagh Bay. • May 1997, 1998, 1999 and 2003 for Pseudo-nitzchia spp. Cell density exceeded 128,000 cells L-1 in 1999. • September 2001 and April 2002, approximately 14000 cells L-1 of Phaeocystis sp.

37. Conclusions • Infauna: Significant community change between 1997-2001. This was mostly associated with huge increases in Pholoe sp. and Abra alba, and a shift towards r-selected strategies. • Epifauna: High abundance of Ascidiella and Asterias in recent years. Major decline in the condition of Modiolus beds between 1999 and 2000 (Green Island/Trawl Zone). Uncertainty about the status of Modiolus cover in 2002 (Trawl Zone). • Phytoplanton: Five important species have had blooms since 1996. The largest bloom involved Pseudo-nitzchia spp. in 1999: cell density exceeded 128,000 cells L-1 and resulted in high Domoic acid accumulations in shellfish.

38. Results: Evenness Community evenness per grab taken at three locations in Strangford Lough between 1993-2002.

39. Results: Richness Species richness per grab for three locations in Strangford Lough (1993-2002).

40. Shellfish toxin analysis 13/08/02 Strangford DPS/PSP neg ASP 0.64 ug/g 01/10/02 Donaghadee DPS/PSP neg ASP 2.24 ug/g 08/05/02 Strangford DPS/PSP neg ASP 0.35 ug/g 07/05/02 Donaghadee DPS/PSP neg ASP 2.10 ug/g

41. Results: Total number of species Total number of species per grab taken at three locations in Strangford Lough (1993-2002). Error bars are 95% confidence limits.