While it is widely believed that oceanographic conditions influence benthic filter-feeding organisms, linkages between water column and population processes on rocky shores have been difficult to document. Here we combine laboratory and field studies to explore the relationship between water column conditions and the feeding, growth and population dynamics of the northern acorn barnacle Semibalanus balanoides. S. balanoides feeding behavior in a flow tank was strongly dictated by flow speeds, food concentrations, and temperatures. The percentage of barnacles feeding increased with both flow speed and food concentrations, but was depressed at high temperatures. These patterns were accurately reflected in S. balanoides feeding in the field. Moreover, within and among populat i o n~, variation in barnacle growth over a wide geographic area directly reflected corresponding variation in flow speed, food abundance, and water temperature. Flow effects on barnacles also had conspicuous population consequences. Since barnacle recruitment and growth are both enhanced at high flow speeds, barnacle density-dependent dynamics may often be strongly affected by flow conditions. Our results suggest that water column processes can powerfully affect passive filter feeding organisms on rocky shores and that oceanographic conditions may often leave a strong signature on the distribution, abundance, and dynamics of assemblages of sessile marine organisms.

Geographic vanahon in secondary production can profoundly influence populahon and community processes yet is rarely studied in benthic manne organisms In this paper w e document stnlung vanahon withln and among locations in the growth and reproducbve output of the acorn barnacle Sernlbalanus balanoides and discuss the potential consequences of our results on understanding recruitment and other population processes Within Narragansett Bay (Rhode Island, USA) barnacle growth and reproduction is far greater than at nearby open coast locations At comparable tidal heights recruits in the Bay grew to nearly twice the basal diameter and had almost 10 times the reproductive output compared to recruits on the open coast Transplant experiments suggest that the high secondary production of Bay barnacles is largely a phenotypic response to high primary production Within-and among-site patterns in barnacle secondary production associated with enhanced flow velocities were also conspicuous Barnacles at low tidal heights, in habitats exposed to large tidal currents and in waveexposed habitats had higher growth and reproduction than barnacles at hlgher tidal heights or habltats with lower velocities Water column food concentrations and fluid velocities both strongly influence barnacle growth and reproduction through their combined effects on the flux of food to indi\~lduals Our results imply that predictable variation in food supply rates may lead to important and equally predictable consequences on regional larval production and the density-dependent dynamics of adult benthic populations

Predators can exert strong controls on community structure through both consumptive and non-consumptive effects. When one of these impacts on diversity is large, such predators have been labeled keystone predators and keystone intimidators respectively. Here we demonstrate that some predators play both roles simultaneously. We studied the species for which the term keystone predator was originally coined, the ochre sea star Pisaster ochraceus. We observed non-consumptive effects that were not mediated through its well-known invertebrate prey, the competitive dominant mussel Mytilus californianus, but instead through whelks Nucella emarginata, another important intertidal predator. Whelks exposed to effluent from stars in the laboratory consumed significantly less, grew significantly less, and developed less reproductive and digestive tissue. Star presence also altered the feeding preferences of whelks. Results suggest these responses are non-linear with respect to the number of predators and thus predator presence may be a larger determinant of non-consumptive effects than density. A second experiment found, in agreement with previous field surveys, that these large non-consumptive effects occurred even though whelk mortality due to consumption by stars is extremely low. These results offer a new mechanism to explain previous field experiments that found whelks have little impact on mussel mortality in the presence of stars yet large effects when stars are absent. They demonstrate the potential for non-consumptive effects to play a major role in community regulation by a keystone predator. They also demonstrate that non-consumptive interactions may have large effects on species even when rates of consumptive mortality are exceedingly low.KEY WORDS: Keystone · Non-consumptive effects · Pisaster · Nucella · Mytilus · Rocky intertidal Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 450: [107][108][109][110][111][112][113][114] 2012 interactions and thus focus on the importance of nonconsumptive effects among species that commonly consume each other (Trussell et al. 2003, Preisser et al. 2005. Less attention has been given to the potential impacts of non-consumptive interactions among predators and rarely consumed prey, or to the potential for predators to simultaneously influence multiple prey species through both consumptive and nonconsumptive effects.Non-consumptive interactions may occur largely in the absence of consumptive interactions in communities where prey possess costly anti-predator adaptations that substantially reduce their risk of consumption but also reduce prey performance . For example, parasitic phorid flies have been shown to reduce foraging behavior by more than 50% in potential ant hosts despite an observed infection level of 3% (Morrison 1999). Predominantly nonconsumptive interactions may also be common in communities where predators encounter a variety of prey that differ in density, handling time, or predator preference ranking, ...

Connectivity among coral reef fish populations is a key factor in governing the structure and dynamics of marine communities and should therefore be taken into account in management and conservation plans. Determining connectivity patterns is a challenging task, since direct tracking of larval trajectories is essentially impossible. During the last decade, however, there have been some significant achievements in the form of indirect tracking of larval sources. Some of these are based on trace elements incorporated into the otoliths of dispersing larvae, which may assist in the identification of natal origins and provide some information about larval trajectories. In this study an attempt was made to infer the dispersal trajectories of larval Chromis viridis (Pomacentridae) that recruit to populations along the northern Gulf of Aqaba (Red Sea). The patterns of trace-element signals found in otoliths (identified by laser ablation inductively coupled plasma mass spectrometry), complemented by the spatial structure in pelagic larval durations (PLD), suggest that the northern populations (i.e. Aqaba and Eilat) of C. viridis are seeded by larvae that disperse along more than one route from sources along the Saudi and Sinai (Egyptian) coasts. The study findings imply that any sound management plans or conservation measures for coral reefs in the Gulf of Aqaba should be regional, and should ideally involve collaboration among all the adjacent countries.

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