THE EFFECTS OF PELAGIC HYDROCARBONS ON THE ROCKY INTERTIDAL FLORA AND FAUNA OF BERMUDA

Abstract

ABSTRACT Over the past decade, the islands of Bermuda have been exposed to an increasing influx of floating pelagic hydrocarbons (“tar balls”). Large quantities of the pelagic tar become stranded on the rocks in the intertidal zone. Tar coverage on the rocks is controlled by the slope of the shore, with the maximum amount accumulating on gently sloping or flat shores. The tar is deposited almost exclusively in the splash zone, and, therefore, the only animals directly affected by the attached tar are those who inhabit and/or feed in this zone. Chemical analyses show that the snails, Nodilittorina tuberculatus and Tectarius muricatus, which live in the splash zone, have the highest hydrocarbon content in body tissue of all animals analyzed. In contrast, all animals sampled from immediately adjacent tide pools contained no petrogenic hydrocarbons. The most abundant life in the intertidal zone is concentrated below this splash zone area of tar accumulation. With few exceptions, the animals from this zone have demonstrated low or zero levels of petrogenic hydrocarbons in the body tissue. The presence of tar on the rocks does not appear to adversely affect reproductive potential, size frequency or abundance of the animals in this intertidal region below the splash zone. The microscopic and macroscopic algae produce very large amounts of biogenic hydrocarbon material. In addition, however, some algal samples from sites of heavy tar accumulation contained high levels of petrogenic hydrocarbons.