The Biology and Ecology of the Invasive Indo-Pacific Green Mussel,

Perna viridis in Kingston Harbour, Jamaica

Dayne Buddo

PhD Candidate

University of the West Indies (Mona)

 

 

In February 1998, green mussels were first observed during the collection of mangrove roots from Kingston Harbour on the south coast of Jamaica by researchers at The University of the West Indies, Mona.

 

It was initially identified as Perna viridis by its shape and colour, as well as the retractor muscle scars on the inside of the shells. The identity was confirmed using chromosome number by scientists at Lamar University, Texas.

 

Much work has been done on the species so far. The density has been tracked over an annual cycle, aspects of the population studied, cage culture growth experiments conducted, gut contents analysed for toxic microalgae, cavity water tested for levels of bacterial coliform, tissues analysed for heavy metals, the island surveyed for establishment and the rate of colonization measured. Work will also be completed shortly on succession in mangrove areas, presence of pesticides in the tissues, spawning and photography of larval development.

 

To date, P. viridis has not been found in any other location in Jamaica. Organisms, such as Perna usually colonize new areas by the release of ballast water by ships as they have a planktonic larval stage. Once these larvae are released, the mussel will establish itself providing that the conditions are favourable for growth and development. These ships that collected ballast from a port where Perna viridis is present simply transported and released the larvae into Kingston Harbour. It is to be noted that it was not a single event, and this release of larval Perna is still being done in Kingston Harbour (see Figure 1).

 

Figure 1: Ship releasing ballast water in Kingston Harbour (D. Buddo)

 

The performance of this mussel and the impacts it has had on the ecology of the area has targeted attention on the unregulated release of ballast water. A ballast water sampling project is now being designed by the Institute of Jamaica to address this problem.

 

Kingston Harbour receives, by far, the highest amount of maritime traffic than anywhere else on the island. It also has numerous places for colonization of the mussel and the high level of organic pollution fosters thriving phytoplankton communities on which the mussel is able to feed and proliferate.

 

The rate of colonization is remarkable in Kingston Harbour. It has been recorded to take just under six weeks to recolonize wharf pilings as high as 90% cover that were stripped manually of all organisms (see Figure 2).

 

Figure 2: Recolonized Wharf Piling (D. Buddo)

 

The growth rate is an equally alarming rate. From results of cage experiments, mussels grew from ~2cm to over 7cm in six months. It is interesting to note that the experiment was not conducted at a station with notable high levels of phytoplankton. The risk of theft of the cages limited the possible stations where the experiment could have been carried out. Other stations would have shown even greater growth rates. Cages were used for the experiment as it allowed easier handling for monthly measurements of the mussel to record the growth rate. However, cages offer lower water circulation rates of phytoplankton than other open substrates such as wharf pilings or ropes. These would have shown a higher growth rate of the mussel. Manipulation of the experiment was limited to a bimonthly removal of fouling organisms from the walls to the cage which would have decreased the circulation of water to the mussels. 

 

Perna viridis poses a potential health hazard if it is to be used for food. Studies have already shown excessively high levels of bacterial coliform in the mussels, though some areas are well within the guidelines for faecal and total coliforms. Preliminary heavy metal analyses have shown that the tissues show no high level of heavy metals that will pose a risk to public health. Further results are now being compiled for review. Analyses of gut contents from mussels collected from various stations around the harbour have shown the presence of four potentially toxic species. All ten (10) stations used in this experiment showed the presence of at least one toxic species and three stations showed all four species.

 

With the high rate of colonization and the exceptionally high rate of growth, Perna viridis is an important invasive species in Kingston Harbour. Ecologically, P. viridis has been documented to dominate its substrate and displace other species. It is an excellent competitor for food and space. The types of substrate that P. viridis has colonized include wharf pilings (wooden {see Figure 3}, concrete and metallic), pier walls, old submerged logs, boats, plastic buckets, PVC pipes, ropes, muddy sea bottoms, submerged rocks, and more ecologically important, seagrass beds and mangrove prop roots (see Figure 4).

 

                              

Figure 3: P. viridis wharf pilings D. Buddo

 Figure 4: Perna viridis on mangrove prop root D. Buddo

            

 Perna viridis is being studied for the first time in Jamaica as a PhD project in the Department of Life Sciences with scheduled completion date in 2005. The first paper on this mussel in Jamaica was published in the Bulletin of Marine Science (Volume 73, number 2, 2003). Strong ties have been made with the Mote Marine Lab (Sarasota, Florida), The United States Geological Survey and Lamar University.

 

This level of invasion is often irreversible; however, proper control measures can and must be put in place to reduce the negative ecological impacts.

 

 

Contact Information: Dayne Buddo

                                     Senior Research Officer

                                     Natural History Division

                                     Institute of Jamaica

                                     10-16 East Street

                                     Kingston, Jamaica

                                     Tel: (876) 922-0620-5

                                     chm.nhd@cwjamaica.com