Exploring patterns of variation in amphipod assemblages at multiple spatial scales: natural variability versus coastal aquaculture effect

Abstract

A 5-factor design survey was carried out to examine the spatial distribution at different scales of amphipod assemblages and sedimentary variables in soft bottoms adjacent to coastal aquaculture installations. Natural variability of sediment variables showed the highest values at the scales of sites (10s of meters) and locality (1 to 10 km), while the greatest component of variation of amphipod assemblages occurred among replicates (on the scale of meters). Regarding the influence of coastal aquaculture, the highest variability of the environmental variables was observed among the different fish farms. On sandy localities, the influence gradient of coastal aquaculture was determined by total free sulphides, whilst, in muddy localities, the main variable was δ 15 N. This study has important consequences for the establishment of a clear and effective methodology for studying and monitoring the impact of fish farming, highlighting the complicated establishment of a widespread pattern of effects by coastal aquaculture. The necessity to apply a high replication effort at several spatial scales, especially at the scales of meters and 10s of meters, to increase the precision of estimates of assemblage composition should be taken into consideration.

Multiscale variability of amphipod assemblages in Posidonia oceanica meadows

“…These results confirm those from previous analyses conducted in marine coastal ecosystems which documented considerable small-scale spatial variation in distributions and abundances of macrozoobenthic populations across a wide range of habitats (Benedetti-Cecchi, 2001b;Coleman, 2002;Underwood and Chapman, 1996), including seagrasses (De Biasi et al, 2003). In particular, amphipod assemblages varied most at the meter scale in the macrophyte Sargassum stenophyllum (Tanaka and Leite, 2003) and in soft bottoms (Fernandez-Gonzalez et al, 2013). Processes potentially involved in such patterns include complex sets of local physical and biological interactions (Anderson et al, 2005;Fraschetti et al, 2005).…”

From paper to practice: an initial approach to implementation of the environmental monitoring plan for fish farming proposed by JACUMAR

“…This variability can affect the sediment mostly at a scale of metres (Quintino et al 2006, Fernandez-Gonzalez et al 2013, as found in this study for some geochemical parameters (pH, finest fraction %, OM and δ 15 N), and for polychaete assemblages. This significant variability at replicate level confirms the well-known importance of selecting a representative sample size in terms of the volume of sampled sediment and the number of replicates (Andrew and Mapstone 1987).…”

Assessment of the impact of Atlantic bluefin tuna farming on Adriatic benthic habitats by analysing macroinvertebrate assemblage structure at family level

“…Amphipods are an important group of benthic fauna in terms of abundance and diversity and are commonly used as indicator because of their greater sensitivity to pollution compared to other crustacea (Sanchez-Jerez & Ramos-Espla, 1996;Gomez-Gesteira & Dauvin, 2000;De-la-Ossa-Carretero et al, 2011;Carvalho et al, 2012). Consequently, previous studies (Fernandez-Gonzalez & Sanchez-Jerez, 2011;Fernandez-Gonzalez et al, 2013) recommend the use of this taxon as a biological indicator of changes potentially resulting from sea bream and sea bass farming activities. Similarly, our results corroborate the usefulness of amphipods as an indicator for monitoring how tuna farming activities affect benthic habitats.…”

“…Despite this, monitoring programs are highly inconsistent between countries, which results in many different approaches and interpretations of their data. However, it is generally accepted that monitoring of benthic habitats is necessary to assess the negative environmental impacts; consequently macrozoobenthic communities are widely selected as a useful indicator because they live in close association with bottom substrata Tomassetti & Porrelo, 2005;Fernandez-Gonzalez et al, 2013). The sea-bed below cages is where contaminant build-up and low-oxygen conditions due to fish farming activities are frequently most critical.…”

“…In such a way, the important role of some local environmental variables for macrofauna is highlighted using this approach. Nevertheless, for a comprehensive understanding of the environmental relationship between tuna farming and faunal changes, further studies are needed on a regional scale, taking into account multispatial scales such as those used by Fernandez-Gonzalez et al (2013) for seabream and seabass farming.…”