Scales of benthic–pelagic coupling and the intensity of species interactions: From recruitment limitation to top-down control

Abstract

Large and usually unpredictable variation in species interaction strength has been a major roadblock to applying local experimental results to large-scale management and conservation issues. Recent studies explicitly considering benthic-pelagic coupling are starting to shed light on, and find regularities in, the causes of such large-scale variation in coastal ecosystems. Here, we evaluate the effects of variation in wind-driven upwelling on community regulation along 900 km of coastline of the southeastern Pacific, between 29°S and 35°S during 72 months. Variability in the intensity of upwelling occurring over tens of km produced predictable variation in recruitment of intertidal mussels, but not barnacles, and did not affect patterns of community structure. In contrast, sharp discontinuities in upwelling regimes produced abrupt and persistent breaks in the dynamics of benthic and pelagic communities over hundreds of km (regional) scales. Rates of mussel and barnacle recruitment changed sharply at Ϸ32°-33°S, determining a geographic break in adult abundance of these competitively dominant species. Analysis of satellite images demonstrates that regional-scale discontinuities in oceanographic regimes can couple benthic and pelagic systems, as evidenced by coincident breaks in dynamics and concentration of offshore surface chlorophyll-a. Field experiments showed that the paradigm of top-down control of intertidal benthic communities holds only south of the discontinuity. To the north, populations seem recruitment-limited, and predators have negligible effects, despite attaining similarly high abundances and potential predation effects across the region. Thus, geographically discontinuous oceanographic regimes set bounds to the strength of species interactions and define distinct regions for the design and implementation of sustainable management and conservation policies.coastal ecosystems ͉ upwelling ͉ community regulation ͉ Chile

Context‐dependent functional dispersion across similar ranges of trait space covered by intertidal rocky shore communities

“…The sites with greater Chl‐ a concentrations also showed warmer waters. Along Chilean shores, and particularly in northern and central regions, the links between nearshore oceanography and coastal ecological processes are strongly related to upwelling activity (e.g., Lagos, Castilla, & Broitman, 2008; Navarrete et al., 2005). In central Chile, for example, upwelling‐related nutrient inputs are associated with greater abundances of corticated algae, but lower abundances of ephemeral algae and grazing effects (Nielsen & Navarrete, 2004).…”

“…Then, niche complementarity should take a larger role in determining species occurrences and abundances, allowing more species to coexist in the less stressful environment (MacArthur & Levins, 1967). Regarding the horizontal variation in community structure, local and mesoscale factors such as productivity, wave exposure, and recruitment variability modulate species abundances and occurrences to lesser extent (Navarrete, Wieters, Broitman, & Castilla, 2005; Roughgarden, Gaines, & Possingham, 1988; Valdivia, Aguilera, Navarrete, & Broitman, 2015). For instance, high wave‐exposure can hamper the grazing activity of low‐intertidal gastropods and sea urchins, allowing for competitive exclusion by algae (e.g., Hawkins & Hartnoll, 1983; Underwood & Jernakoff, 1981, 1984).…”

Complexity and simplification in understanding recruitment in benthic populations

“…The pelagic environment, which modulates food delivery and larval supply to bottom environments, then links benthic systems at even larger spatial scales (e.g. Noda 2004, Navarrete et al 2005. Thus, dynamics of nearshore benthic populations reflect at least four types of processes: (1) larval pool dynamics, including larval feeding environment dispersal away from adults, (2) larval transport, (3) settlement, and (4) post-settlement biotic processes, including larval production ( Fig.…”

Mesoscale advection of Upogebia pusilla larvae through an upwelling filament in the Canaries Coastal Transition Zone (CTZ)

“…Various authors have attributed the variations in recruitment of intertidal sea urchins, barnacles, mussels and crabs to oscillations in upwelling strength (Ebert and Russell 1988;Roughgarden et al 1988;Connolly and Roughgarden 1998;Navarrete et al 2005;Palma et al 2006;Broitman et al 2008). They observed lower recruitment rates near capes and headlands, preferred sites of upwelling filaments.…”