Spatial variation in size and density of adult and post-settlement Semibalanus balanoides: effects of oceanographic and local conditions

Abstract

Regional oceanographic processes are emerging as strong influences on growth and recruitment of intertidal species, with important consequences for populations. Yet local conditions such as wave exposure are also important. To disentangle these effects for the intertidal barnacle Semibalanus balanoides, we surveyed 259 sites around Scotland in July and August over 6 yr (from 2001 to 2006). Scaled digital photographs at 3 shore levels gave sizes and densities of juvenile and adult barnacles for comparison with wave fetch, remotely sensed chlorophyll a (chl a) concentration and seasonal sea surface temperature (SST). Patterns were also compared with site 'openness': the area of connected open sea < 30 km away. Patterns at the 3 shore levels were similar. Hierarchical partitioning (HP) showed that survey year had the biggest effect and improved the predictive power of other variables: wave fetch for adult and juvenile densities, chl a for juvenile size and openness for adult size. SST had little effect. Regression models selected using information theoretic measures included positive effects of chl a, varying among surveys, on average size of barnacles (R 2 from 0.5 to 0.6), and larger high shore barnacles in greater wave exposure. Population densities of adults and juveniles increased with wave fetch, with chl a only influencing density at high shore levels (R 2 from 0.1 to 0.4). Despite temporal and spatial variation in responses to chl a and wave fetch among surveys, relationships were consistent with growth and size in S. balanoides being limited by food supply, and increased recruitment and adult densities in increased wave exposure. Large-scale ecological patterns in this rocky intertidal species thus result from large-scale oceanographic effects on food concentration with habitat-scale wave-mediated effects on supply of food and larvae. 398: 207-219, 2010 where such features dominate , while local wind-driven flows influence settlement rate (e.g. Hawkins & Hartnoll 1982). Patterns of current flow ultimately result in site-specific transport patterns, as described by dispersal kernels (Aiken et al. 2007), and thus determine population connectivity (Pineda et al. 2007). (2) Oceanographic conditions influence phytoplankton productivity, and this affects feeding success and energy content of dispersing planktotrophic larvae, with continuing effects on postsettlement survival (Emlet & Sadro 2006). In filter feeders such as barnacles, post-settlement growth rates are increased by higher phytoplankton biomass (Menge et al. 1997, Sanford & Menge 2001, while size-specific egg numbers and thus fecundity are also dependent on food supply . (3) At ocean scales, current-driven heat fluxes structure regional climates, with consequent effects (e.g. El Niño) that often trump smaller scale influences of oceanographic conditions on coastal marine systems. KEY WORDS: Phytoplankton · Wave exposure · Growth · Recruitment · Semibalanus balanoides Resale or republication not permitted without written consent of the ...

Connectivity and population repatriation: limitations of climate and input into the larval pool

“…Together these examples indicate that variation in input into the larval pool can drive variation in connectivity and illustrate the need to incorporate variation in larval pool input into models of marine population connectivity. They also illustrate the need for a mechanistic understanding of the forces generating variation in adult input into the larval pool; in the study by Smith et al (2009), recruitment was correlated with upstream adult biomass, while in Hughes et al (2000) adult abundance only explained 1.2% of the variation in recruitment and fertility accounted for 72% of the variance.A striking commonality between this study and those by Hughes et al (2000), Smith et al (2009), Reed et al (2009), and Burrows et al (2010 is that in 181 Mar Ecol Prog Ser 495: 175-183, 2014 all cases, a significant relationship was found between adult inputs into the larval pool and recruitment, even though these studies placed little emphasis on measuring, or even identifying, the other forces that potentially shape population connectivity between larval release and recruitment. Overall, input into the larval pool plays a key role in population connectivity, as it provides the initial starting conditions for subsequent modification by other factors (physical transport, mortality, behavior).…”

“…Mar Ecol Prog Ser 495: [175][176][177][178][179][180][181][182][183] 2014 of variation in recruitment (Hughes et al 2000, Reed et al 2009, Burrows et al 2010) and metapopulation growth (Carson et al 2011).…”

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

“…On the other hand, if larval supply and phytoplankton dynamics are controlled by the same features, as it was explained in the previous paragraph, peaks in chlorophyll-a concentrations and setlement rates will occur simultaneously (e.g., Ref. [20]). …”

“…On the other hand, if larval supply and setlement are enabled by less favorable conditions for phytoplankton, the luctuations in the rates of larval processes may be negatively related to the concentrations of chlorophyll-a. Evidences of both trends were registered for rocky shore invertebrates in several regions [20,21,73]. Although the oceanographic and ecological processes that afect community dynamics are similar at the rocky shores, the correlation degrees between phytoplankton abundance and larval processes vary among sites and taxa.…”

“…Because of that, variations in the rates of the ecological processes of rocky shore invertebrates are commonly correlated with luctuations in chlorophyll-a concentration in the ocean (e.g., Refs. [17][18][19][20]). These numerical relationships are important tools to ecological modeling, and may be used to improve stock management in some extent [21].…”