Benthic macrofaunal biodiversity in relation to sediment sulfide concentration under salmon farms in southwestern New Brunswick, Bay of Fundy B.D. Chang, J.A. Cooper, F.H. Page, and R.J. Losier Fisheries and Oceans Canada Science Branch, Maritimes Region St. Andrews Biological Station 531 Brandy Cove Road St. Andrews, NB, Canada E5B 2L9 2017 Canadian Technical Report of Fisheries and Aquatic Sciences 3202 1 Canadian Technical Report of Fisheries and Aquatic Sciences Technical reports contain scientific and technical information that contributes to existing knowledge but which is not normally appropriate for primary literature. Technical reports are directed primarily toward a worldwide audience and have an international distribution. No restriction is placed on subject matter and the series reflects the broad interests and policies of Fisheries and Oceans Canada, namely, fisheries and aquatic sciences. Technical reports may be cited as full publications. 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Les demandes de rapports seront satisfaites par l'établissement auteur dont le nom figure sur la couverture et la page du titre. Les numéros 1 à 456 de cette série ont été publiés à titre de Rapports techniques de l'Office des recherches sur les pêcheries du Canada. Les numéros 457 à 714 sont parus à titre de Rapports techniques de la Direction générale de la recherche et du développement, Service des pêches et de la mer, ministère de l'Environnement. Les numéros 715 à 924 ont été publiés à titre de Rapports techniques du Service des pêches et de la mer, ministère des Pêches et de l'Environnement. Le nom actuel de la série a été établi lors de la parution du numéro 925. 1 Canadian Technical Report of Fisheries and Aquatic Sciences 3202 2017 Benthic macrofaunal biodiversity in relation to sediment sulfide concentration under salmon farms in southwestern New Brunswick, Bay of Fundy by B.D. Chang, J.A. Cooper, F.H. Page, and R.J. Losier Fisheries and Oceans Canada Science Branch, Maritimes Region St. Andrews Biological Station 531 Brandy Cove Road St. Andrews, NB, Canada E5B 2L9 This is the three hundred and twenty-fourth Technical Report of the St. Andrews Biological Station, St. Andrews, NB ii Her Majesty the Queen in Right of Canada, 2017 Cat. No. Fs 97-6/3202E-PDF ISBN 978-0-660-07640-9 ISSN 1488-5379 Correct citation for this publication: Chang, B.D., Cooper, J.A., Page, F.H., and Losier, R.J. 2017. Benthic macrofaunal biodiversity in relation to sediment sulfide concentration under salmon farms in southwestern New Brunswick, Bay of Fundy. Can. Tech. Rep. Fish. Aquat. Sci. 3202: v + 71 p. iii TABLE OF CONTENTS Abstract ...................................................................................................................................... iv Résumé ....................................................................................................................................... iv Introduction ................................................................................................................................. 1 Methods....................................................................................................................................... 2 Results ......................................................................................................................................... 5 Discussion ................................................................................................................................. 10 Conclusions ............................................................................................................................... 17 Acknowledgements ................................................................................................................... 19 References ................................................................................................................................. 19 Tables ........................................................................................................................................ 24 Figures....................................................................................................................................... 34 Appendix A: Sulfide concentration data ................................................................................... 47 Appendix B: List of taxa ........................................................................................................... 48 Appendix C: Effect of sampling unit size on diversity measures ............................................. 52 Appendix D: Effect of using higher taxonomic levels on diversity measures .......................... 64 iv ABSTRACT Chang, B.D., Cooper, J.A., Page, F.H., and Losier, R.J. 2017. Benthic macrofaunal biodiversity in relation to sediment sulfide concentration under salmon farms in southwestern New Brunswick, Bay of Fundy. Can. Tech. Rep. Fish. Aquat. Sci. 3202: v + 71 p. Benthic sediment samples were collected under two marine salmon farms (sites A & B) and a reference site (C) in southwestern New Brunswick (SWNB), Bay of Fundy. Triplicate grab samples were taken at 6 stations at each site. Macrofaunal biodiversity and total free sulfide concentration were measured in each grab. Mean sulfide concentrations per station ranged from 139-1266 µM at farm A, 650-3550 µM at site B, and 67-129 µM at reference site C. Univariate diversity indices (number of taxa, Shannon diversity index, Margalef’s species richness index, and Pielou’s evenness index) indicated that the macrofaunal biodiversity under both farms was impacted by organic enrichment, with higher impacts at the larger farm (site B). There were clear indications of adverse effects on benthic macrofaunal biodiversity at sulfide concentrations above ~1500 µM and some indications of impacts at lower sulfide concentrations. A simple linear regression between the number of taxa and the sulfide concentration per station was not significant (p=0.11). Macrobenthic diversity was highest in sediments with intermediate sulfide concentrations, and lowest in sediments with higher sulfide concentrations. The biodiversity under reference site C was lower than under moderately enriched site A for some indices. Capitella spp. were low in abundance or absent at site C, while at the two farms, their abundance increased at intermediate sulfide concentrations, then decreased at higher sulfide concentrations. Sample variability associated with elevated sulfide concentrations indicated that sample size was an increasingly important considerations when evaluating relative impacts at higher concentrations. Ordination of the biodiversity data through multi-dimensional scaling (MDS) indicated that reference site C was distinct from the two farm sites, while there was some overlap between the two farm sites. Capitella spp. was the taxon that contributed the most to similarity within the farm sites (but not at the reference site) and to dissimilarity between all pairs of sites. There were also significant differences in biodiversity among sulfide classes. Capitella spp. was the taxon that contributed most to similarity within sulfide classes (except Oxic A) and to dissimilarity between pairs of sulfide classes (except Oxic A–Hypoxic B). The results generally agree with previous studies on the relationship between biodiversity and sediment sulfide concentration at fish farms in SWNB. Studies on the effects of sampling unit size and the level of taxonomic indentification on biodiversity measures are included as appendices. RÉSUMÉ Chang, B.D., Cooper, J.A., Page, F.H., and Losier, R.J. 2017. Benthic macrofaunal biodiversity in relation to sediment sulfide concentration under salmon farms in southwestern New Brunswick, Bay of Fundy. Can. Tech. Rep. Fish. Aquat. Sci. 3202: v + 71 p. Des échantillons de sédiments