2014. Recruitment facilitation and spatial pattern formation in soft-bottom mussel beds. Ecosphere 5(12):160. http://dx.Abstract. Mussels (Mytilus edulis) build massive, spatially complex, biogenic structures that alter the biotic and abiotic environment and provide a variety of ecosystem services. Unlike rocky shores, where mussels can attach to the primary substrate, soft sediments are unsuitable for mussel attachment. We used a simple lattice model, field sampling, and field and laboratory experiments to examine facilitation of recruitment (i.e., preferential larval, juvenile, and adult attachment to mussel biogenic structure) and its role in the development of power-law spatial patterns observed in Maine, USA, soft-bottom mussel beds. The model demonstrated that recruitment facilitation produces power-law spatial structure similar to that in natural beds. Field results provided strong evidence for facilitation of recruitment to other musselsthey do not simply map onto a hard-substrate template of gravel and shell hash. Mussels were spatially decoupled from non-mussel hard substrates to which they can potentially recruit. Recent larval recruits were positively correlated with adult mussels, but not with other hard substrates. Mussels made byssal thread attachments to other mussels in much higher proportions than to other hard substrates. In a field experiment, mussel recruitment was highest to live mussels, followed by mussel shell hash and gravel, with almost no recruitment to muddy sand. In a laboratory experiment, evenly dispersed mussels rapidly self-organized into power-law clusters similar to those observed in nature. Collectively, the results indicate that facilitation of recruitment to existing mussels plays a major role in soft-bottom spatial pattern development. The interaction between large-scale resource availability (hard substrate) and local-scale recruitment facilitation may be responsible for creating complex power-law spatial structure in soft-bottom mussel beds.

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Sea turtles spend much of their life in aquatic environments, but critical portions of their life cycle, such as nesting and hatching, occur in terrestrial environments, suggesting that it may be important for them to detect sounds in both air and water. In this study we compared underwater and aerial hearing sensitivities in five juvenile green sea turtles (Chelonia mydas) by measuring auditory evoked potential responses to tone pip stimuli. Green sea turtles detected acoustic stimuli in both media, responding to underwater stimuli between 50 and 1600 Hz and aerial stimuli between 50 and 800 Hz, with maximum sensitivity between 200 and 400 Hz underwater and 300 and 400 Hz in air. When underwater and aerial hearing sensitivities were compared in terms of pressure, green sea turtle aerial sound pressure thresholds were lower than underwater thresholds, however they detected a wider range of frequencies underwater. When thresholds were compared in terms of sound intensity, green sea turtle sound intensity level thresholds were 2–39 dB lower underwater particularly at frequencies below 400 Hz. Acoustic stimuli may provide important environmental cues for sea turtles. Further research is needed to determine how sea turtles behaviorally and physiologically respond to sounds in their environment.

Incomplete baseline data on population demographics and patterns of habitat use and the unmet need for international coordination of conservation actions are among the challenges inherent in promoting the recovery of endangered, migratory marine species. Working with field researchers, government officials and conservationists we developed a comprehensive atlas of all known sea turtle nesting grounds (n = 1311 discrete sites), including colony size and protection frameworks, in the 43 nations and territories in the Wider Caribbean Region (WCR). The majority of sites hosted extremely small colonies characterized by < 25 nesting crawls yr −1 per species. Large nesting colonies were rare. Sites with > 500 nesting crawls yr −1 comprised between <1 and 8% of species-specific nesting site totals. We identified information gaps, including sites where nesting was known to occur but data were insufficient to categorize nesting colony size. The database allows users to identify and rank critical habitat, fill data gaps, inform policy-making, promote the implementation of regional agreements, and strengthen national and international conservation planning and research. This research highlights the value of international networking and data sharing, the benefits of collecting baseline information on the distribution and abundance of populations, and the usefulness of long-term, systematic monitoring of sea turtle nesting grounds.