Seascapes are spatially defined areas containing marine habitats interconnected due to their proximity and through the exchange of fauna, detritus, and nutrients. A considerable amount of research has determined the significance of spatial subsidies in ecosystems with relatively low in situ production, yet some studies indicate that this may also occur between two highly productive systems, such as seagrass meadows and macroalgal reefs. Kelp is regularly eroded and dislodged from reefs throughout the year which can become entrapped in adjacent seagrass meadows, resulting in a bio-available nutrient source, thus providing a spatial subsidy. This detrital kelp is preferentially fed on by seagrass-inhabiting mesograzers, allowing for the transfer of nutrients into higher trophic levels. Additionally, detritus can act as an attractant to mesograzers through increased habitat complexity, though disentangling the trophic and habitat effects is difficult, and to date there has been little evidence that this has a trophic benefit.
This project aims to determine the trophic effects of allochthonous detrital kelp in Posidonia sinuosa seagrass meadows in Shoalwater Islands Marine Park. Field sampling within Shoalwater Islands Marine Park will be completed across a temporal scale to assess the faunal assemblage in Posidonia meadows, and its consistency over time. Additionally, an in-situ experiment aims to explore whether kelp within seagrass meadows influence mesograzer growth, fecundity, biomass, and densities, and to disentangle the mechanisms which drive changes in mesograzer assemblage.