Loss or gain? The complex role of thermophilic aliens in fast-warming seas where heat-sensitive natives collapse

Dr Gil Rilov¹, Dr Tamar Guy-Haim¹, Ohad Peleg¹, Eerz Yeruham¹

¹Israel Oceanographic and Limnological Research (IOLR), Haifa, Israel

Bioinvasions and climate change can be closely linked as drivers of biodiversity change, especially in fast-warming ocean regions. In such regions, populations of natives sensitive to warming may collapse, and with them, some ecological functions may be lost. Simultaneously, thermophilic aliens are boosted, and those with traits similar to the collapsing natives, might compensate for the loss of functions. The southeastern Mediterranean is fast-warming region (2-3oC), and is also a invasion hotspot of thermophilic species from the IndoPacific. On shallow reefs in the region, dozens of once-abundant native non-harvested invertebrate species collapsed, and aliens completely dominate some groups. We tested the thermal performance of native and alien invertebrates and macroalgae and found that in most cases aliens have a much higher optimum temperature than natives. In the field, incubation experiments showed that communities dominated by declining native brown-algae meadows have much higher biodiversity, biomass and metabolic functions than the now expansive turf barrens overgrazed by invasive herbivores rabbitfish, while areas covered by an increasingly dominate alien red algae “shrub” functioning is shifted from overall autotrophic to heterotrophic. Mesocosm experiments showed that under warming and acidification conditions, the brown-algae community itself becomes more heterotrophic, and more dominated by alien species (but richness did not change). These dramatic alterations in functions mean that the reefs are going through a regime shift to a novel ecological state that will intensify in the future and probably spread westward, but some functions lost by the collapse of sensitive aliens may be regained by aliens.

Biography:

Gil Rilov received his PhD from Tel- Aviv University in 2002 for his research on ecological aspects of species interactions on Mediterranean rocky shores. Between 2000-2008 he conducted ecological research on Atlantic and Pacific coral and rocky reefs as part of his post-doc periods as well as serving as a science coordinator of the Partnership of Interdisciplinary Studies of Coastal Oceans (PISCO) project at Oregon State University. In 2009, at IOLR Gil established and headed the Marine Community Ecology Lab since 2009, and is head the Marine Biology Department since 2016. He have been studying the ecology of coastal communities (coral reefs, rocky shores and recently, seagrass) for the past 27 years in many biogeographic regions (Mediterranean, Red Sea, Pacific and Atlantic and Caribbean coasts). This includes ecological surveys and field and lab experiments on benthic-pelagic coupling (larval recruitment), species interactions, biodiversity and more. Gil  edited a Springer book on Marine Bioinvasions. Gil’s lab runs the National Monitoring Program on rocky shore biodiversity for the past 9 years, and investigates the ecology and biodiversity of Mediterranean coastal communities, and the effects of bioinvasions, climate change (warming, acidification, sea level rise and extreme events), fishing and marine protected areas on these communities and their functions. As part of a BaltMed project with GEOMAR (Kiel, Germany), Gil’s lab has constructed several innovative experimental setups (including a mesocosm facility) to test the effects of warming and acidification on species, communities and ecosystem functions.