Coastal Upwelling Drives Intertidal Assemblage Structure and Trophic Ecology

Abstract

Similar environmental driving forces can produce similarity among geographically distant ecosystems. Coastal oceanic upwelling, for example, has been associated with elevated biomass and abundance patterns of certain functional groups, e.g., corticated macroalgae. In the upwelling system of Northern Chile, we examined measures of intertidal macrobenthic composition, structure and trophic ecology across eighteen shores varying in their proximity to two coastal upwelling centres, in a hierarchical sampling design (spatial scales of >1 and >10 km). The influence of coastal upwelling on intertidal communities was confirmed by the stable isotope values (δ13C and δ15N) of consumers, including a dominant suspension feeder, grazers, and their putative resources of POM, epilithic biofilm, and macroalgae. We highlight the utility of muscle δ15N from the suspension feeding mussel, Perumytilus purpuratus, as a proxy for upwelling, supported by satellite data and previous studies. Where possible, we used corrections for broader-scale trends, spatial autocorrelation, ontogenetic dietary shifts and spatial baseline isotopic variation prior to analysis. Our results showed macroalgal assemblage composition, and benthic consumer assemblage structure, varied significantly with the intertidal influence of coastal upwelling, especially contrasting bays and coastal headlands. Coastal topography also separated differences in consumer resource use. This suggested that coastal upwelling, itself driven by coastline topography, influences intertidal communities by advecting nearshore phytoplankton populations offshore and cooling coastal water temperatures. We recommend the isotopic values of benthic organisms, specifically long-lived suspension feeders, as in situ alternatives to offshore measurements of upwelling influence.

Habitat coupling writ large: pelagic‐derived materials fuel benthivorous macroalgal reef fishes in an upwelling zone

“…), consumer diet and community structure (Reddin et al. ), and here, our data indicate that the bottom up supply of basal resources drives secondary production in macroalgae‐dominated reef foodwebs. Our data highlight the complexity of open ecosystems (Polis et al.…”

“…Although we did not directly measure isotopes from primary producers in this study, a study undertaken in the Antofagasta region by our group (Reddin et al. ) and subsequent unpublished work on the same indicator taxa supports our assumption. Bivalves sampled in the identical location as those shown here were isotopically most similar to POM, whilst grazing gastropods had δ 13 C and δ 15 N values close to that of macroalgae.…”

Trophic relationships between the large scyphomedusa Chrysaora plocamia and the parasitic amphipod Hyperia curticephala

“…Considering that pelagic phytoplankton, macroalgae and benthic microalgae are the main sources of primary production in this area (Reddin et al 2015) and the fact that C. plocamia (Ceh et al 2015) and hyperiid amphiods (Fleming et al 2014) may use benthic resources, samples of macroalgae, particulate organic matter (POM) and benthic algae/biofilm were collected from subtidal locations on the Mejillones peninsula adjacent to Mejillones Bay to include them as potential energy sources in our analysis. Epilithic biofilm was scraped from rocks using a metal spatula, a 5 l water sample was collected for POM, and fronds of the dominant brown alga (Lessonia nigrescens) were collected, with tissue taken from frond areas of recent growth.…”

Chlorophyll-a and the Supply Side Ecology: Lessons from the Rocky Shores

“…[69,70]. Even sites within the same bay or just less than 1 km apart may present high contrasts in recruitment rates as a consequence of diferences in the phytoplankton dynamics [71].…”