With coastal sea temperature predicted to increase 1.5-2°C by 2050, it is important to assess how the communities of coastal marine habitats will respond, in order to predict overall biodiversity and ecosystem level impacts. In this study I used the novel technology of heated settlement panels which heated the surface of each panel and a thin layer of overlying water to 1°C or 2°C above ambient temperatures, thus mimicking oceanic warming predictions for 2050 (IPCC, 2014). This technology was used to assess the effects of in situ elevated warming on benthic early community development.
In a first experiment, panels were deployed at the BAS Rothera Research station, Antarctica for a period of 18 months. To evaluate whether the encrusting species had acclimated to the warmer temperatures, I performed upper thermal limit and heat shock experiments on one of the main benthic colonisers, the spirorbid worm Romanchella perrieri. These data indicated a lack of both acclimation and a heat shock response in this species. This suggested that R. perrieri were resisting at the higher temperatures rather than successfully acclimating. An RNA-Seq approach was also was with another major spirorbid coloniser, Protoleospira stalagmia. The transcriptome data suggested the gradual shutting down of cellular pathways in the organisms in the 2°C treatment, supporting the observations of lack of acclimation in R. perrieri. Biofilm analyses were also carried out on the same panels. In contrast to the invertebrate results, there were very few differences observed in the microbial community across experimental treatments. Thus indicating that microbial communities may be more robust in the face of future climate change compared with metazoans.
In a second experiment, these panels were deployed in a temperate region, the Menai Strait, Wales. Development of the communities was monitored on a seasonal basis over a period of 13 months. Whilst communities varied seasonally, there was no significant difference in overall composition or species biodiversity between treatments. The exception to this was the overlapping evaluations in June 2015 and June 2016. Overall percentage cover was higher in June 2016 compared with June 2015, compromising three dominant species: the barnacle Balanus crenatus, the encrusting worm Spirobranchus triqueter and the bryozoan Electra pilosa.
Furthermore species composition was different in June 2016 and June 2015 was different in the control panels compared to the heated panels. Thus in warmer years even a +1°C or a +2°C
temperature rise can significantly affect temperate benthic ecosystems, producing a thermal tipping point for some species. These data validate the application of this heated settlement panel technology in temperate ecosystems.