3 research outputs found
Growth and ecophysiology of two Antarctic benthic predators; Isotealia antarctica and Urticinopsis antarctica
Get PDFThere is a dearth of basic life history and physiological data from Southern Ocean species, particularly from benthic vagile predators. This is an important data gap because species inhabiting the Southern Ocean live in a more temperature stable but seasonally varying environment than temperate and tropical counterparts. For many species living below 0 âŠC for a significant proportion of the year, bodily functions are slowed to disproportionately lower rates than would be predicted by temperature alone. Certain life history and physiological processes are often aligned with the short summer season of productivity. However, predators may behave differently because they are decoupled from the phytoplankton bloom and some have been shown to exhibit less
seasonal physiological change. To further our understanding of Antarctic predator growth and seasonal ecophysiology, field growth rates were measured for two soft-bodied Antarctic anemone benthic predators, Isotealia antarctica and Urticinopsis antarctica, using in situ sampling of anemones on uniquely marked tiles. Ex situ measurements of oxygen consumption and seven-day faecal output were obtained from recently collected specimens in aquaria and compared between summer and winter. Winter physiological data for Antarctic species are rare, and we tested the hypothesis that generalist feeders or predators continue to feed during the winter. Growth rates differed between species and between years. I. antarctica and U. antarctica both exhibited overall positive field growth rates across a 15 month period between 2020 and 2021; with U. antarctica increasing 199.80% (± SE 25.8) in mass compared to a 16.85% (± SE 8.9) increase in I. antarctica. There was no significant difference in I. antarcticaâs growth between 15 and 25 months field deployment. After 25 months, I. antarctica showed an average 7.96% (± SE 8.05) increase in buoyant weight. Ex situ oxygen consumption and faecal egestion did not differ seasonally, which, demonstrates that anemones fed at similar rates during the winter and summer. In contrast to some members of the Antarctica benthos, I. antarctica and U. antarctica actively feed all year round, whereas several other species have been reported to enter a state of torpor in winter
Climateâdriven substitution of foundation species causes breakdown of a facilitation cascade with potential implications for higher trophic levels
Get PDF1. Climate change can alter ecological communities both directly, by driving shifts in species distributions and abundances, and indirectly by influencing the strength and direction of species interactions. Within benthic marine ecosystems, foundation species such as canopy -forming macro-algae often underpin important cascades of facilitative interactions.
2. We examined the wider impacts of climate-driven shifts in the relative abundances of foundation species within a temperate reef system, with particular focus on a habitat cascade whereby kelp facilitate epiphytic algae that in turn facilitate mobile invertebrates. Specifically we tested whether the warm water kelp Laminaria ochroleuca, which has proliferated in response to recent warming trends, facilitated a secondary habitat-former (epiphytic algae on stipes) and associated mobile invertebrates, to the same degree as the cold water kelp Laminaria hyperborea.
3. The facilitative interaction between kelp and stipe-associated epiphytic algae was dramatically weaker for the warm water foundation species, leading to breakdown of a habitat cascade and impoverished associated faunal assemblages. On average, the warm water kelp supported >250 times less epiphytic algae (by biomass) and >50 times fewer mobile invertebrates (by abundance) than the cold water kelp. Moreover, by comparing regions of pre and post range expansion by L. ochroleuca, we found that warming-impacted kelp forests supported around half the biomass of epiphytic algae and one-fifth of the abundance of mobile invertebrates, per unit area, compared with unimpacted forests. We suggest that disruption to this facilitation cascade has the potential to impact upon higher trophic levels, specifically kelp forest fishes, through lower prey availability.
5. Synthesis. Climate-driven shifts in speciesâ distributions and the relative abundances of foundation organisms will restructure communities and alter ecological interactions, with consequences for ecosystem functioning. We show that climate-driven substitutions of seemingly similar foundation species can alter local biodiversity and trophic processes in temperate marine ecosystems
