In late August 1978, a red tide occurred in Roaringwater Bay / Long Island Bay, near Sherkin Island Marine Station, an event that would see the Marine Station monitoring the phytoplankton of Roaringwater Bay / Long Island Bay and South of Sherkin Island, Co Cork, for the next 36 years.
From 1978, the programme evolved through an initial exploratory phase, with a particular focus on the toxic species threatening the local fishery, before establishing a series of 12 coastal water positions, known as “stations”, for monitoring all species. These stations were visited every 10 to 12 days from April to October, weather permitting. Water samples were taken at set depths at each site, down to 50m at the deepest sites, and fixed with Lugol’s iodine. Supplementary data on weather and sea conditions, sea temperature, salinity, conductivity, water clarity, and time of high tide were recorded. Back at the laboratory, smaller samples were settled in chambers and prepared for identification and counting of species present.
The unique dataset presented here contains quantitative data on the phytoplankton species recorded in seawater samples for Roaringwater Bay / Long Island Bay and South of Sherkin. It comprises a long-term record from 1980 to 2014 encompassing over 34,000 samples and at least 440,000 counts of phytoplankton species, together with over 34,400 seawater temperatures, and 28,000 salinity measurements. In all, over 350 phytoplankton taxa were recorded and identified to species where possible with reference to the literature available at that time.
In addition to the standardized dataset from Roaringwater Bay / Long Island Bay and South of Sherkin Island presented here, other phytoplankton studies were made in separate areas along the southwest coast, mainly Bantry Bay, with much smaller studies from Dunmanus Bay, Cork Harbour, the gas rig off the Old Head of Kinsale, as well as some exploratory data from Roaringwater Bay / Long Island Bay and South of Sherkin prior to 1980. While the extent of species identification (for example sometimes aimed at only a few toxic species) varied according to the aims of these other studies, these data do provide additional information and it is hoped to make these available at a future date.
What are Phytoplankton?
Phytoplankton are microscopic marine algae that form the base of the food chain in the ocean.
The most well-known aspects of phytoplankton studies are those relating to the “Red Tides” that have occurred. “Red Tide” is the name given to the phenomenon in which a population explosion or “bloom” takes place in a phytoplankton population. This usually results in the discoloration of the water, which may be tinged with red (although other colours can be produced, depending on the pigmentation of the microscopic marine algae). The environmental and economic implications of certain species of phytoplankton have stimulated extensive research over the years. Some species contain toxins, which can become concentrated in filter-feeding animals such as mussels. Severe consequences can arise when humans eat contaminated shellfish. Many species are also responsible for fish kills around the world. Species of special interest are Karenia mikimotoi (Gyrodinium aureolum), Dinophysis acuminata and D. acuta, as they have been responsible for some outbreaks around south-west Ireland.