Effects of Sediment Disturbance by the Heart Urchin Echinocardium cordatum on the Sediment–Seawater Solute Exchange: An Exclusion Experiment

Date
2024-07-12
Authors
McLeod, Roen
Simone, Michelle
Vopel, Kay
Supervisor
Item type
Journal Article
Degree name
Journal Title
Journal ISSN
Volume Title
Publisher
AIMS Press
Abstract

Spatangoid heart urchins are dominant bioturbators in marine soft-sediment ecosystems worldwide. Their repeated sediment reworking prevents biogeochemical sediment stratification and colonization by other species, with implications for sedimentary reaction processes that affect the local sediment–seawater solute exchange. Here, we used a simple exclusion experiment to investigate how a subtidal Echinocardium cordatum population (18.2  6.7 individuals m−2), foraging at an individual speed of ~45 cm per day affects the sediment–seawater solute exchange. To do so, we removed all heart urchins from eight one-meter-diameter areas of the 10-m deep seafloor of Man O’War Bay, Hauraki Gulf, New Zealand, and prevented recolonization and thus sediment reworking for 56 days. Subsequently, we measured the sediment–seawater exchange of O2, NO3–, NO2–, NH4+, and N2 both within and outside the exclusion areas, under light or dark conditions, and found no difference. The absence of a legacy effect of foraging E. cordatum after their removal suggests that, at least in this habitat, their influence on the sediment–seawater solute exchange may be limited to sediment being displaced in the immediate surrounding of the urchin. This unexpected result underlines the importance of evaluating the influence of bioturbators on the sediment–seawater solute exchange in the context of local environmental conditions, animal behavior, and population characteristics.

Description
Keywords
bioturbation, sediment–water solute exchange, oxygen, nitrogen , 3704 Geoinformatics , 3705 Geology
Source
AIMS Geosciences, ISSN: 2471-2132 (Print); 2471-2132 (Online), AIMS Press, 10(3), 1-14. doi: 10.3934/geosci.20240xx
Rights statement
© 2024 the Author(s), licensee AIMS Press. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0)