Monday, April 18, 2016

Measuring settlement rates of sea urchins. New paper out!

by Owen Wangensteen

Team members of the ChallenGen Project at the University of Barcelona, in collaboration with scientists from the University of La Laguna (Canary Islands) have just published a new paper on Scientia Marina journal, describing and testing new designs of artificial collectors for quantitative assessment of settlement rates in sea urchins.

The study of population dynamics of sea urchins is crucial for understanding the ecology of Mediterranean and temperate Atlantic rocky shores, since these echinoderms are often the main herbivore species in shallow benthic ecosystems and they are responsible of linking the primary production from seaweeds to other higher levels of the trophic chains. Many sea urchin populations may be limited by the settlement rates (the process by which the planktonic sea urchin larvae settle and become juvenile sea urchins). Methods for measuring these settlement rates were not standardized and yielded non-comparable results. The work presented in this paper, carried out in parallel at Canary Islands and Costa Brava (Spain) shows that three-dimensional collectors made from “bioballs” (a biofilm-friendly, high surface material often used as filters in aquaria) are the most suitable device for this assessment, allowing for an accurate and repeatable measurement of this elusive, yet important, ecological process.

The best part is that these bioballs collectors are useful not only for sea urchins settlers. They could be suitable for assessing settlement and colonization rates for a wide-range of marine invertebrates and can help marine biologists to get a more accurate view of the population dynamics of many species present in benthic ecosystems.

The three types of collector tested in this work: plastic biofilter ball (A, C), vertical brush (B, D) and horizontal triangular mat of coconut fibre (B, E).