Benthic community structure and spatiotemporal thermal regimes in two upwelling ecosystems: Comparisons between South Africa and Chile

Abstract

On the basis of 16-yr satellite time series (1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003) of sea surface temperature (SST) and using univariate and multivariate statistical techniques, we quantified patterns of fluctuation in oceanographic conditions, as well as their spatial structure along the coasts of South Africa and Chile between 29.0u and 34.5uS. Since variations in environmental conditions over multiple timescales are driven by oceanographic-atmospheric processes modulated by coastal morphology, all of which affect in different ways coastal organisms, we hypothesized that dynamic properties of the environment contribute to characteristic patterns on rocky intertidal biomass structure across upwelling ecosystems. Although long-term mean temperatures were similar between coasts, the relative importance of annual, semiannual, intraseasonal, and high-frequency SST fluctuations differed; South Africa is more strongly pulsed over shorter timescales. Similar spatial discontinuities in thermal regimes were observed, with changes at about 32uS. Multivariate summaries of benthic community structure derived from functional group biomasses revealed striking differences between South Africa and Chile, as well as between regions north and south of 32uS within each ecosystem. Between-continent and regional-scale differences in community structure were largely unrelated to mean SST, but correlated with the different measures of temporal variance in SST. For all functional groups, as well as aggregate measures of benthic community composition, the weekly to annual SST fluctuations explained large fractions (.35%) of biological variability. Results highlight the importance of quantifying the temporal variance of regimes of hydrographic conditions since multispecies assemblages are expected to respond in different ways to the driving oceanographic processes behind these fluctuations.

Interactive effects of grazing and environmental stress on macroalgal biomass in subtropical rocky shores: Modulation of bottom-up inputs by wave action

“…Thinly filamentous and single-layer foliose algae, characterized by high mass-specific productivity (Littler and Littler, 1980;Nielsen and Sand-Jensen, 1990;Steneck and Dethier, 1994) and the ability to rapidly colonize bare spaces at mid to upper intertidal levels (Littler and Littler, 1980;Lubchenco and Gaines, 1981), are a seasonal to semi-permanent component of rocky shore communities along most of the temperate regions of the world (Hawkins and Hartnoll, 1983a;Jenkins et al, 2008;Poore et al, 2012;Wieters et al, 2009). These algal groups are collectively known as 'ephemerals' because they build up dense patches that develop rapidly, and frequently collapse within a few months.…”

Functional community structure of shallow hard bottom communities at Easter Island (Rapa Nui)

“…We categorized species into one of 8 (benthic) or 5 (fish) functional groups based on a) morphological and anatomical traits related to maximum possible rate of biomass production (mass-specific growth; ability to quickly assimilate nutrient availability) and resistance to herbivory [algae; largely following Steneck & Dethier (1994) with grouping modifications similar to Broitman et al (2001) and Wieters et al (2009) Randall & Cea (2011)]. Benthic: 1) ephemeral algae, 2) corticated algae, 3) leathery algae, 4) crustose algae, 5) corals, 6) filter feeders, 7) herbivores, and 8) predators.…”

“…and spatial cover of sessile species (e.g., corals, macroalgae, sponges, barnacles, etc.) at shallow (<8 m), mid (10-15 m), and deep (17-23 m) zones were quantified at 2-3 rocky reefs using the standard transect-quadrat method, as described in detail in Wieters et al (2009). A minimum of ten 0.25 m graphed.…”

Successional trajectory of the fouling community on a tropical upwelling ecosystem in southeast Rio de Janeiro, Brazil

“…The third aspect is temperature variation, one of the most important factors for the regulation of biological processes in ectothermic organisms (KORDAS et al, 2011). Therefore, these aspects may play an important role in the successional process of benthic communities (MCCOOK; CHAPMAN, 1997;MENGE et al, 2004;WIETERS et al, 2009).…”

“…A large number of studies on the interface between benthic ecology and oceanography have identified a number of the major coastal phenomena that can control or shape the organization of benthic communities (reviewed by WIETERS et al, 2009). Coastal upwelling is one of these phenomena, and it occurs when deep, cold and nutrient-rich waters reach the surface near the coast (VALENTIN, 1987).…”