Quantifying the Consumption of Algal Wrack with Dry Weight Analysis
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Description
Algal wrack (marine algae deposited on shorelines) is an important source of food and shelter for many organisms. By calculating the mass of wrack consumption it's contribution to intertidal food webs may be assessed. Wrack consumption can be quantified by determining the total loss of biomass through time. Samples of giant kelp (Macrocystis pyrifera) were placed on isolated sections of Black's Beach, San Diego, California and collected after 1, 3, 7, 12, and 21-day intervals. Wrack samples were cleaned using a sieve and deionized water, dried in a drying oven at 60°C, and weighed to within 0.01g to determine their final biomass. This value was compared to expected dry weights determined by an equation derived for the same taxa by Wickham et al., 2019. The difference between measured and expected dry weights was used to determine the amount of biomass consumed by organisms. The results of this study were inconclusive, as dry weight actually increased through time. Typically, consumption rates of algal wrack are highest during the first few days of exposure with continued consumption over time. It appears there was a propagation of error in our study, likely due to the methodology for cleaning the samples prior to analysis. Specifically, we suspect that the presence of residual sediment within dry samples increased with sample age, as more degraded samples could not be as effectively rinsed. Future algal wrack studies should quantify the effect of residual sediment, possibly by combusting the samples, before using expected dry weight calculations and models.
Quantifying the Consumption of Algal Wrack with Dry Weight Analysis
Algal wrack (marine algae deposited on shorelines) is an important source of food and shelter for many organisms. By calculating the mass of wrack consumption it's contribution to intertidal food webs may be assessed. Wrack consumption can be quantified by determining the total loss of biomass through time. Samples of giant kelp (Macrocystis pyrifera) were placed on isolated sections of Black's Beach, San Diego, California and collected after 1, 3, 7, 12, and 21-day intervals. Wrack samples were cleaned using a sieve and deionized water, dried in a drying oven at 60°C, and weighed to within 0.01g to determine their final biomass. This value was compared to expected dry weights determined by an equation derived for the same taxa by Wickham et al., 2019. The difference between measured and expected dry weights was used to determine the amount of biomass consumed by organisms. The results of this study were inconclusive, as dry weight actually increased through time. Typically, consumption rates of algal wrack are highest during the first few days of exposure with continued consumption over time. It appears there was a propagation of error in our study, likely due to the methodology for cleaning the samples prior to analysis. Specifically, we suspect that the presence of residual sediment within dry samples increased with sample age, as more degraded samples could not be as effectively rinsed. Future algal wrack studies should quantify the effect of residual sediment, possibly by combusting the samples, before using expected dry weight calculations and models.