Partial congruence in habitat patterns for taxonomic and functional diversity of fish assemblages in seagrass ecosystems
Marine conservation aims to maintain ecological functioning through the protection of biodiversity, frequently relying on habitat categories as representative surrogates for biodiversity. Habitat biodiversity surrogates typically represent taxonomic diversity, despite species functional traits being more directly linked to ecosystem functioning. Here, we evaluate habitat biodiversity surrogates based on taxonomic and functional diversity of fish assemblages in seagrass ecosystems of Nova Scotia, Canada. We do so by assessing congruence in habitat differences (i.e., seagrass vs adjacent bare soft sediment) between biodiversity components across varying environmental conditions, and also by identifying relationships of fish biodiversity with environmental, habitat, and landscape variables. We found only partial agreement in habitat differences for each biodiversity type, that is, habitat differences in taxonomic diversity were only sometimes reflected by functional diversity. In fact, taxonomic diversity was consistently higher in seagrass than bare sediment, while this was not always the case for functional diversity. Similar functional diversity between habitat types resulted from redundancy in functional traits and consistent expression of dominant traits. Regression analyses indicated that taxonomic diversity was determined by habitat complexity (canopy height, sediment organic content), wave exposure, and seagrass bed size (R2 ~ 0.60). Functional diversity was determined by habitat complexity (shoot density, canopy height, and sediment organic content) and wave exposure (R2 = 0.475), suggesting the importance of environmental filtering in selecting a certain set of functional traits. Our study suggests that multiple biodiversity components combined with knowledge of the environmental context are necessary for optimal use of habitat biodiversity surrogates in conservation planning.
We thank G. Bugden, M. Bravo, M. Dowd, C. Giroux, M. Humble, S. Roach, J. Rowsell, and D. Smith for assistance in field sampling, and O. Brown (Natural Resources Canada, Bedford Institute of Oceanography) for assistance in processing sediment samples for particle size. We are grateful for comments provided by reviewers that improved the manuscript. Funding was provided by Fisheries and Oceans Canada.
Compliance with ethical standards
Conflict of interest
All authors declare no conflict of interest.
All applicable international, national, and institutional guidelines for the care and use of animals were followed (DFO/CFIA Animal Care File #13-21) and all appropriate research permits were obtained (DFO FRN M13-14, DFO Registration/Fishing Licence 7-000153-26).
- Fishbase (2016) Froese R, Pauly D (eds). World Wide Web electronic publication. www.fishbase.org, version. Accessed Oct 2016
- Jackson EL, Rowden AA, Attrill MJ, Bossey SJ, Jones MB (2001) The importance of seagrass beds as a habitat for fishery species. Oceanogr Mar Biol 39:269–303Google Scholar
- Scott WB, Scott MG (1988) Atlantic fishes of Canada. University of Toronto Press and Fisheries and Oceans Canada, Supply and Services CanadaGoogle Scholar
- SeaLifeBase (2016) Palomares MLD, Pauly D (eds) World Wide Web electronic publication. www.sealifebase.org, version. Accessed Oct 2016
- Shore Protection Manual (1975) Fort Belvoir VA: US Army Coastal Engineering Research Center, vol 1Google Scholar
- Wong MC, Dowd M, Bravo M (2016) Nekton in Zostera marina (eelgrass) beds and bare soft-sediment bottom on the Atlantic coast of Nova Scotia, Canada: species-specific density and data calibrations for sampling gear and day-night differences. Canadian Technical Report of Fisheries and Aquatic Sciences, Report number: 3155. https://doi.org/10.13140/RG.2.1.3587.7368