Sea urchins on beach in Bequia
News
March 12, 2021
Hundreds of white sea urchins wash up on beach in Bequia

Questions remain following two mass die-offs of ‘sea eggs’ in a localized area in the Bequia harbour between last week and this week.

Residents of the Grenadine island first noticed hundreds of dead white sea urchins, known scientifically as the Tripneustes ventricosus, between Thursday, March 4 and Saturday, March 6, with the majority seen last Friday.

So far, the event has so far only been confirmed on the beach in front of the Bequia Plantation Hotel.

The Fisheries Division of the Ministry of Agriculture, Forestry and Fisheries were expected to make two visits to the site this week to carry out assessments of the area and various tests.

However, the sea urchins that lined the beach after the first die-off were said to have been removed by the end of the weekend.

While this was hoped to have been a one-off event, picture evidence taken yesterday, March 11, has shown that more sea urchins have washed up on the same beach.

Joshua Gooding , who holds a bachelor’s degree in biology with specializations in marine biology and ecology and environmental biology, has been monitoring the situation.

He conducted an initial analysis of the die-off last weekend which took into consideration that research on white sea urchins is limited, and, also that his analysis was done in the absence of certain unknown factors.

Gooding listed strong wave action, toxins or pollutants, a rise in environmental temperatures and disease/pathogens as possible contenders for the why that still has to be answered with regard to this mass mortality event.

His strongest contender was disease, and there was a speculation as to whether illegal change of ballast water or dumping of sewage in the water could have caused an infection among the urchins.

On Tuesday, urchins with pink pigmentation on their spines were observed in the area close to the beach, while healthy urchins were observed closer to the wharf. Gooding noted unusual behaviour among the creatures in that some urchins near to rocky substrate by the beach where the die off occurred were not attached to the rock, and were not maintaining a grip when assisted.

Following these observations, more urchins washed up on the same beach two days later.

This has led Gooding to feel strongly that it is indeed a pathogen.

A cause for puzzlement is also why the urchins collected in that area.

In a publication by the Food and Agricultural Organization of the United Nations on the white sea urchin, compiled by fisheries biologists in 2010, there is some general information about the species.

“In general, urchin health and urchin diseases are not well understood or well defined in the scientific literature, particularly in the light of the possibility of significant regional differences. However, urchin populations do experience periodic die-offs. Environmental stress is known to be a significant variable in these episodes, but the specific stressors and their mode of operation within urchin populations are unknown,” they write.

However, in the mass die-offs from disease recorded in the publication, there were complete or significant loss of spines.

The publication also notes, “Gametes and embryos of white sea urchins are known to be negatively affected by elevated levels of a number of toxicants, including phosphates, nitrates, sewage effluent and stormwater runoff, and by increased temperature.”