Habitat traits and predation interact to drive abundance and body size patterns in macroalgae associated fauna
Data files
Oct 10, 2023 version files 670.42 KB
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Epifauna_BodySizeData.csv
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HabitatUnit_MorphologyData.csv
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README.md
Abstract
Habitat-forming organisms provide three-dimensional structure that supports abundant and diverse communities. Variation in the morphological traits of habitat-formers will therefore likely influence how they facilitate associated communities, either via food and habitat provisioning, or by altering predator-prey interactions. These mechanisms, however, are typically studied in isolation and thus we know little of how they interact to affect associated communities. In response to this, we used naturally occurring morphological variability in the alga Sargassum vestitum to create habitat units of distinct morphotypes to test whether variation in the morphological traits (frond size and thallus size) of S. vestitum, or the interaction between these traits, affect their value as habitat for associated communities in the presence and absence of predation. We found morphological traits did not interact, instead having independent effects on epifauna that were negligible in the absence of predation. However, when predators were present, habitat units with large fronds were found to host significantly lower epifaunal abundances than other morphotypes, suggesting large frond alga provided low-value refuge from predators. The presence of predators also influenced the size structure of epifaunal communities from habitat units of differing frond size suggesting the refuge value of S. vestitum was also related to epifauna body size. This suggests that habitat-formers may chiefly structure associated communities by mediating size-selective predation, and not through habitat-provisioning. Furthermore, these results also highlight that habitat traits cannot be considered in isolation, for their interaction with biotic processes can have significant implications for associated communities.
README
Title of Dataset: "Habitat traits and predation interact to drive abundance and body size patterns in associated fauna".
"HabitatUnit_MorphologyData.csv"
Dataset of morphology traits for the seaweed, Sargassum vestitum, used to create habitat units of specific morphotypes to test for the relative influence of frond size and thallus size in structuring the invertebrate communities associated with seaweed in the presence and absence of predators.
Column name descriptions
- “Caging treatment” = the caging treatment that strand of algae was exposed to; “full” = fully caged treatment where predators were excluded; “none” = uncaged treatment where predators had full access to habitat units; “half” = open cages used as a cage control for the experiment. “Single” = single strand habitat units that were used to test for the effect of thallus size on invertebrate communities and were excluded from the caging experiment.
- “Patch_ID” = unique identifier for each patch used to deploy habitat units (four habitat units were deployed per patch)
- “Sample_ID” = unique identifier for each habitat unit. First character represents caging treatment (F – full cage, N = uncaged, H = open cage); second character is meaningless; third character represent frond size (S = small; L = large); forth character is used to distinguish between replicates within treatments.
- “Sample_ID2” = unique identifier for each strand. First character represents caging treatment (F – full cage, N = uncaged, H = open cage); second character is meaningless; third character represent frond size (S = small; L = large); forth character is used to distinguish between habitat unit replicates within treatments; firth character is used to distinguish between individual strands used in double strand habitat units.
- “herbivory” = binary value (Y/N) of whether habitat units experienced herbivory during the experiment
- “Epiphytes” = if epiphytes were present at the conclusion of the experiment
- “Alga_biomass” = weight of algal strand in grams
- “Alga_surface_area” = surface area of algal strand in mm2
- “Frond_ID” = identifies individual fronds (10 in total) taken from each strand for morphological trait measurement
- "F_Area" = frond area in mm2
- "F_Perim" = frond perimeter in mm2
- "F_length" - maximum length of frond in mm2
“Epifauna_BodySizeData.csv”
Dataset of body length measurements for each individual macroinvertebrate that colonised habitat units.
Column name descriptions
- “Patch_ID” = unique identifier for each patch used to deploy habitat units (four habitat units were deployed per patch)
- “Caging treatment” = the caging treatment that strand of algae was exposed to; “full” = fully caged treatment where predators were excluded; “none” = uncaged treatment where predators had full access to habitat units; “half” = open cages used as a cage control for the experiment.
- “Sample_ID” = unique identifier for each habitat unit. First character represents caging treatment (F – full cage, N = uncaged, H = open cage); second character is meaningless; third character represent frond size (S = small; L = large); forth character is used to distinguish between replicates within treatments.
- “Branch ID” = Unique identifier to distinguish between individual strands used in double strand habitat units.
- “Org_ID” – Identifies individual invertebrates from each community.
- “Taxa” = taxonomic classification (usually down to order only).
- “Len_micro” = maximum body length measurement of individual in micrometres.
Sharing/access Information
Was data derived from another source? No
Methods
To test whether habitat unit size (i.e., algal biomass/thallus size) interacted with frond size diversity (small, large and mixed mean frond size) to affect the abundance and size structure of associated communities, we created and deployed five types of habitat units: a single branch with small fronds, a single branch with large fronds, two branches with small fronds, two branches with large fronds and a unit with one branch with small fronds and one branch with large fronds (hereafter ‘mixed frond’ in text and ‘mix’ in plots).
To test how variation in algal morphology and predation risk structure epifaunal communities, we used an orthogonal design with predation risk (three levels) and habitat unit morphology (three levels, as only double-branched habitat units were used); with 6 replicates for each combination level.
After five days, all algae were retrieved by snorkelling. Each branch was collected separately by removing cage (if present), then the cable tie at the attachment point and quickly placing each branch of the habitat unit in a jar underwater (i.e., for double-branched habitat units branches were placed in separate jars). Back in the laboratory, all jars were stored in the refrigerator (~2 °C) until processing (maximum three days). Digital zooplankton scanner technology was then used to count and measure (total body length: µm) all epifauna.