Скачать или смотреть Are these Tasmanian barrens now more like NSW barrens than the kelp beds beside them?

New research by IMAS scientists shows that urchin-affected reefs on Tasmania’s east coast now function much like those further north in New South Wales, with similar species and grazing patterns. The study, published in Marine Environmental Research, explored how climate-driven warming and sea urchin grazing are reshaping southern reef ecosystems.

The team compared kelp beds and urchin barrens at twenty reef sites across both states. Using underwater surveys and herbivory experiments, they tested whether community differences were greater between regions or between habitat types. They fixed small pieces of kelp and other algae either raised off the bottom for fish access only, or flat on the reef where both fish and urchins could graze.

The study found that the main factor shaping which species live on a reef (its structure) and how they interact through feeding and grazing (its functioning) was the type of habitat. Whether it was a healthy kelp bed or an urchin barren had a much stronger influence than where the reef was located.

Overall, the same habitat type on a different reef a thousand kilometres apart shared more similar species and grazing patterns than different habitat types on the same reef, 100s of meters apart.

The longspined sea urchin, Centrostephanus rodgersii, emerged as the main species driving these patterns. Where these urchins were abundant, kelp pieces fixed flat on the reef surface were eaten more, showing strong grazing pressure. In contrast, pieces suspended just above the bottom, accessible only to fish - were left mostly intact. This elegant experiment showed that most of the grazing and tropicalisation impacts on these reefs is driven by urchins rather than fish.

Paper title: Sea urchin herbivory drives subcontinental similarity of tropicalizing reefs