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Shallow, coastal lagoons are vulnerable to eutrophication and harmful algal blooms, often due to the loss of benthic suspension feeders. Florida Bay, USA, is a sub-tropical lagoon that has suffered from a series of ecological disturbances, including cyanobacterial blooms, loss of seagrass habitat, and widespread sponge mortality. A field study was executed at sites across Florida Bay to investigate effects of cyanobacterial blooms of the genus Synechococcus on the suspensionfeeding loggerhead sponge Spheciospongia vesparium. In situ measurements of loggerhead sponge survival, water pumping rates, and particle retention were made over the course of a year under both bloom and non-bloom conditions and for naturally-occurring and transplanted sponges. The mortality of transplanted loggerhead sponges significantly increased following cyanobacterial blooms. Sponge water pumping rates, particle retention, and filtration rates were depressed in areas where cyanobacteria blooms were present. When loggerhead sponge community filtration rates were compared with cyanobacteria intrinsic growth rates, sites with low abundances of sponges had persistent, dense blooms and harbored positive net growth rates for cyanobacteria (0.78 to 1.45 d −1 ). In contrast, sites with high abundances of sponges had few or no blooms and net growth rates for cyanobacteria that were slow or negative (−0.17 to 0.24 d −1 ). This suggests that the loss of filtration from sponge mortality in Florida Bay has contributed to the persistence of algal blooms. Restoration of benthic suspension feeders such as sponges could be an important management tool to mitigate algal blooms in shallow coastal lagoons, although survival of transplanted populations will likely require concurrent improvement of water quality by other means since blooms inhibit sponge pumping, particle retention, and filtration.KEY WORDS: Florida Bay · Sponges · Spheciospongia vesparia · Loggerhead sponge · Cyanobacteria · Synechococcus · Harmful algal bloom Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 451: [31][32][33][34][35][36][37][38][39][40][41][42][43] 2012 2001), the loss of benthic suspension feeders from such a system likely represents a more significant loss of top-down control than for deeper, well-flushed ecosystems.Florida Bay, USA, is a shallow, sub-tropical lagoon between mainland Florida and the Florida Keys; it is the largest estuary in Florida, valuable for recreation and fisheries, and adjacent to the sensitive habitats of the Florida Keys National Marine Sanctuary and Everglades National Park. Since the late 1980s, Florida Bay has been affected by a series of ecological disruptions, including sponge die-offs (Butler et al. 1995), blooms of the cyanobacteria Synechococcus spp. (Phlips et al. 1999), and seagrass mortality (Robblee et al. 1991). The root cause of these disturbances may be linked to human alterations of the freshwater flow in the Everglades, which is upstream of Florida Bay (Phlips e...

Locomotion of infaunal bivalve mollusks primarily consists of vertical movements related to burrowing; horizontal movements have only been reported for a few species. Here, we characterize hard clam walking: active horizontal locomotion of adults (up to 118 mm shell length, SL) of the commercially important species, Mercenaria mercenaria, at the sediment surface—a behavior only briefly noted in the literature. We opportunistically observed walking over a 10-yr period, at 9 different sites in the Peconic Bays, New York, USA, and tested several hypotheses for the underlying cause of this behavior through quantitative field sampling and reproductive analyses. Hard clam walking was exhibited by males and females at equal frequency, predominantly during June/July and October, when clams were in peak spawning condition. Extensive walking behavior appears to be cued by a minimum population density; we suggest it may be mediated by unidentified pheromone(s), infaunal pressure waves and/or other unidentified factors. There was no directionality exhibited by walking clams, but individuals in an area of extensive walking were highly aggregated and walking clams were significantly more likely to move toward a member of the opposite sex. Thus, we conclude that hard clam walking serves to aggregate mature individuals prior to spawning, thereby facilitating greater fertilization success. In the process of investigating this behavior, however, we apparently oversampled one population and reduced clam densities below the estimated minimum threshold density and, in so doing, suppressed extensive walking for a period of >3 years running. This not only reinforces the importance of detailed field investigations of species biology and ecology, even for those that are considered to be well studied, but also highlights the need for greater awareness of the potential for research activities to affect focal species behavior.