Relative influence of processes structuring fjord deep-water macrofaunal communities across multiple spatial scales

Abstract

We examined the processes that maintain spatially subdivided deep-basin macrobenthic communities in a New Zealand fjord. Based on previously reported quantitative taxa distribution data, we measured physical and biological processes acting at the sample scale (physical and nutritional sediment characteristics, predation), basin scale (disturbance, productivity, local connectivity) and the fjord scale (connectivity to the regional species pool). Using partial redundancy analysis (RDA), we partitioned their effects on community variability. Direct gradient analysis revealed that previously reported high-, medium-and low-diversity communities are similarly grouped according to their position along measured biotic and abiotic gradients, where 36% of community variation in niche space (i.e. after effects of distance along the fjord were removed) was explained by the full model. Variance partitioning showed that basin-scale factors explained the highest amount of variation in basin communities, followed by sample-scale and fjord-scale factors. Sample-and basin-scale factors were correlated. Examination of the residual component of community variation showed that further investigation into basin-scale processes is warranted. These data support the notion of multiscaled control of community dynamics. Fjords may be unique in representing an 'ecotone' type habitat demonstrating processes at similar scales to those maintaining shallow soft-sediment communities, and those of deep-sea systems. Furthermore, this analysis may understate the importance of connectivity to the regional species pool (fjord-scale process) in such habitats where local extinctions may be relatively frequent.KEY WORDS: Macrofauna · Fjord · Spatial scale · Ecotone · Predation · Connectivity · Trophic · Disturbance Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 425: [175][176][177][178][179][180][181][182][183][184][185][186][187][188][189][190][191] 2011 Fjord marine habitats are often classified as estuaries based on hydrography and geomorphology (Ketchum 1983, Burrell 1988. However, fjords may also be deep (often greater than 500 m water depth) and comparatively stable over time (Pickrill 1987, Syvitski et al. 1987, reflecting deeper offshore habitats (Grant 2000, Snelgrove & Smith 2002. This suggests that community structure and related processes may span a broad range of spatial scales. Within shallow water soft-sediment communities, species pattern often shows strong spatial structure over scales of metres to 100s of metres (Thrush 1991), where biotic and abiotic processes acting over such scales are thought to be important in structuring local communities. Such processes may include microhabitat dynamics affecting interactions between individuals (e.g. Edgar & Barrett 2002), water-driven mechanical and chemical sediment processes (e.g. Probert 1984, Guichard & Bourget 1998, disturbance by benthic megafauna (e.g. Parry et al. 2003), and effects of 'ecosystem engineers' (e.g. Berkenbusch...

The VENUS cabled observatory as a method to observe fish behaviour and species assemblages in a hypoxic fjord, Saanich Inlet (British Columbia, Canada)

“…Physiography, hydrography (including deep-water renewal), and weather are the most important factors shaping fjord ecosystems habitats (Nordberg 2001) and consequently strongly influence the benthic community structure (Renaud et al 2007;Blanchard et al 2010;Brewin et al 2011). Limited circulation and isolation of deep basins in silled glacial fjords limit nutrient exchanges and larval dispersal (Renaud et al 2007), leading to low carbon fluxes and thus low faunal abundances and biomasses (Blanchard et al 2010).…”

“…The structure of marine benthic communities is controlled over multiple interrelated spatial and temporal scales (Levin 1992;Brewin et al 2011). While seasonal patterns and interannual variations have been widely studied using ship-based sampling (e.g., Nordberg 2001;Blanchard et al 2010;Glover et al 2010), we have a limited understanding of small-scale variability of benthic communities in marine environments, especially at depths over 50 m. Furthermore, ecological observations resulting from punctual sampling often neglect biological rhythm frequencies, misleading our understanding of community and ecosystem dynamics (Morgan 2004).…”