Organic enrichment and structure of macrobenthic communities in the glacial Baker Fjord, Northern Patagonia, Chile

Abstract

In this study we describe community parameters such as densities, biomasses, species composition, feeding modes and normalized biomass size-spectra (NBSS) of macrobenthic invertebrate communities from three stations located in the Baker Fjord obtained on four seasonal campaigns in 2008 and 2009. The macrobenthic communities were dominated by small-bodied polychaetes (Paraonidae, Capitellidae and Cirratulidae) characterized by continuous year-round breeding, short life-spans, and fast turnover rates, which in turn regulated the standing stock in the communities. Principal component analysis and multiple-regression analysis demonstrate the distribution of macrobenthic communities in the study area to be mainly controlled by few local environmental conditions. Macrofaunal densities, diversity and feeding modes were significantly correlated with the total organic carbon (TOC; R2 = 0.74; P < 0.001) and chlorophyll-a (Chl-a; R2 = 0.55; P < 0.05) content in the sediments. This study also suggests that feeding modes and NBSS can be used to detect and follow possible changes caused by natural perturbations such as glacial lake outburst floods or anthropogenic stressors associated with ecological impacts generated by the construction and operation of hydroelectric power stations in the Baker River.

Larval fish assemblages from channels and fjords of south Pacific Patagonia: effects of environmental conditions

“…Horizontal, vertical and chemical stratification is found in the fjord habitats of southern Chile. The estuarine and benthic ecology of benthic populations is shaped by seasonal physical disturbances of natural origin that are associated with river discharge resulting from melting ice and the release of suspended particulate material (Vargas et al 2011, Quiroga et al 2012, Landaeta et al 2013, Zenteno et al 2014.…”

Latitudinal consistency of biomass size spectra - benthic resilience despite environmental, taxonomic and functional trait variability

“…Thus, our study supports the notion that quality rather than quantity of food determines the level of benthic productivity. As reported in numerous studies, sediment pigment concentration, which represents the 'freshly produced' fraction of organic matter in sediments and can be a measure of ecosystem productivity, was linked with higher biomass [51][52][53] . The relationship between δ 13 C and benthic standing stock is less obvious, especially in this study, where we reported higher standing stock in fjords characterized by lower δ 13 C values.…”

Seasonal constancy (summer vs. winter) of benthic size spectra in an Arctic fjord

“…However, it must be noted that comparisons of intercept (treated as a proxy of total biomass) are only possible when spectra represent similar size class range (Hua et al 2013). The intercepts of NBSS plotted for Kongsfjorden fauna were higher than those reported by most other studies (Saiz-Salinas and Ramos 1999;Quiroga et al 2005Quiroga et al , 2012Quiroga et al , 2016, but similar to those of the communities inhabiting highly productive regions and sediments with high organic matter content (Akoumianaki et al 2006;Hua et al 2013). But it must be noted that these differences in intercepts may result from various sampling gears used and not overlapping size classes with our studies.…”

“…The functioning of a system (e.g., productivity, rate of the energy flow through trophic levels) may be reflected in the size spectra characteristics. The intercept of NBSS can be an indicator of total biomass in the community (Sprules and Munawar 1986;Quiroga et al 2012) or a rate of primary production in the system in case of pelagic systems (Zhou 2006). However, it must be noted that comparisons of intercept (treated as a proxy of total biomass) are only possible when spectra represent similar size class range (Hua et al 2013).…”

“…Moreover, the slope coefficient reported in this study also suggests lack of disturbances. Disturbances, e.g., extensive fishing (Graham et al 2005), eutrophication (Quiroga et al 2012), or low oxygen levels (Quiroga et al 2005), cause elimination of large organisms and promotion of small size classes (and the size spectra slope steepening).…”