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Algal Wracks and Biological Abundance

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Algal wrack mats, conglomerations of seaweed on sandy beaches, are important drivers of biodiversity on San Diego beaches. They provide an integral food source and habitat to many species, both terrestrial and marine. However, many beach communities remove the algal wracks to clear the beaches for recreational use which may have important ecological implications for the sandy beach communities. This study examined how algal wrack affected invertebrate species in the sediment underneath the algal wrack. We tested the hypothesis that biological abundance would increase with the amount of algal wrack. Replicate wrack mats of giant kelp were placed for 21 days during August 2018 on Black's Beach in La Jolla, CA. Sand samples were collected with a 30cm diameter corer which penetrated 20cm into the sediment. Cores were collected both underneath the mats, and from a paired control spots 1 meter away on days 1, 3, 7, 12 and 21. Coleoptera were the most abundant organisms collected during this study. Species abundance was universally higher underneath the wrack than in control plots. This could be caused by the cooler and wetter structure created for organisms, and the food the wrack provided. This study calls for further analysis of beach grooming for human recreational use and its implications on biological diversity.

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Algal Wracks and Biological Abundance

Algal wrack mats, conglomerations of seaweed on sandy beaches, are important drivers of biodiversity on San Diego beaches. They provide an integral food source and habitat to many species, both terrestrial and marine. However, many beach communities remove the algal wracks to clear the beaches for recreational use which may have important ecological implications for the sandy beach communities. This study examined how algal wrack affected invertebrate species in the sediment underneath the algal wrack. We tested the hypothesis that biological abundance would increase with the amount of algal wrack. Replicate wrack mats of giant kelp were placed for 21 days during August 2018 on Black's Beach in La Jolla, CA. Sand samples were collected with a 30cm diameter corer which penetrated 20cm into the sediment. Cores were collected both underneath the mats, and from a paired control spots 1 meter away on days 1, 3, 7, 12 and 21. Coleoptera were the most abundant organisms collected during this study. Species abundance was universally higher underneath the wrack than in control plots. This could be caused by the cooler and wetter structure created for organisms, and the food the wrack provided. This study calls for further analysis of beach grooming for human recreational use and its implications on biological diversity.