We conducted a series of food choice experiments using detritus from cultured eelgrass (Zostera marina) genotypes (clones) as a food source and either one or a combination of the following invertebrate grazers: the tube dwelling amphipod Ampithoe lacertosa, the free swimming isopod Idotea resecata, and/or the tube building polychaete Platynereis bicanaliculata.
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All feeding trials were conducted by placing pre-weighed fragments of each choice (approximately 4 cm in length) in 140 mL cups (7 cm tall, 6 cm diameter) covered with a 250 um mesh cloth and submerged in a flowing seawater bath in an indoor tank. Food choices were marked using colored zip ties, and trials were terminated before any food item was reduced in size by one half. Consumption was calculated as ([Hi X Cf/Ci] - Hf ), where Hi and Hf were initial and final wet masses of tissue exposed to consumers, and Ci and Cf were initial and final masses in controls.
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In addition to feeding trials, we grew invertebrates for one month (in similar containers and feeding trial conditions) with food sources that varied in number of seagrass clones present. Animal survival was assessed weekly, and food was replaced.
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The chemical traits for individual eelgrass clones were also assessed. We measured the pressure required to penetrate and tear each genotype. We clamped in place below a needle (17G / 19mm length), which was held in place with a metal sleeve and which supported a cup to which dry sand was added a few milligrams at a time until the pin pierced completely through the plant tissue. The mass of the dry sand and the apparatus were then weighed to determine the mass needed to pierce the leaf (Duffy & Hay 1991). Tensile strength was measured using a tensiometer. Leaf segments were clamped to a hanging balance equipped with a maximum mass indicator and pulled by hand until the leaf failed. Phenolic content was determined on an approximately 4 mg subsample using a modified Folin-Ciocalteu method (see Bolser et al. 1998). An approximately 3 mg subsample was analyzed for carbon and nitrogen concentration on a Thermo Flash EA 1112 Soil elemental analyzer.
In this project, we examined the effect of eelgrass genetic and invertebrate species diversity on detrital consumption and animal survival rates in a series of laboratory experiments. This dataset contains chemical traits for individual eelgrass clones and feeding rates for each grazer type (isopods, amphipods, polychaetes).
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Abstract:
\nSeagrass meadows are among the world's most productive ecosystems, and as in many other systems, genetic diversity is correlated with increased production. However, only a small fraction of seagrass production is directly consumed, and instead much of the secondary production is fueled by the detrital food web. Here, we study how plant genotype influences detrital consumption. We used three common mesograzers\u2014an amphipod,\u00a0Ampithoe lacertosa, an isopod, Idotea resecata, and a polychaete,\u00a0Platynereis bicanaliculata. Each grazer consumed eelgrass detritus at rates greater than live eelgrass or macroalgae. This detrital consumption, however, was not spread evenly over leaves shed from different eelgrass clones.\u00a0Palatability and consumption varied because of genotype specific differences in leaf texture, secondary metabolites (phenolics), and nutritional quality (nitrogen). Further, detritus derived from some eelgrass genotypes was palatable to all grazers, while detritus from other genotypes was preferentially consumed by only one grazer species.
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These data are illustrated in figures 2 and 3 of the manuscript:
\nReynolds LK, KM Chan, E Huynh, SL Williams, and JJ Stachowicz (in press) Plant genotype indentity and diversity interact with mesograzer species diversity to influence detrital consumption in eelgrass meadows.\u00a0DOI:10.1111/oik.04471
BCO-DMO Processing:
\n- separated original Excel file into 3 datasets: feeding trials, biodiversity experiments, invertebrate survival;
\n- modified parameter names to conform with BCO-DMO naming conventions: replaced % with pcnt, replaced spaces with underscores.