Biological impact of scuba diving on the abundance and composition of marine phyla in the benthic zone in Lake Grevelingen.
At the age of fifteen, I (Julia) joined a scuba diving team in the Netherlands. After becoming a divemaster at the age of eighteen, I discovered the endless possibilities of working in the dive industry and from that moment on, the divine plan of my life unfolded. Since my first breaths taken underwater, my passion for diving and love of the ocean have only increased. Although at the same time, I also witnessed the problems and challenges the ocean is facing.
After eight years of working as a dive instructor, I felt the urge to further develop my skills and knowledge in order to be able to explore new ways of ocean conservation. As a result, I decided to study marine biology in my home country of the Netherlands. For my final research project during my bachelor studies in Biology, I went back to the place where I first experienced the marine world: Lake Grevelingen. Recently, scuba diving in Dutch lakes has increased in popularity and participation, which could soon impact these frequented locations. In Zeeland alone, an estimated 800.000 dives are done on a yearly base. Scuba divers are not supposed to interfere with the marine environment, a practice generally taught during dive operations, but unfortunately this is not always upheld by individual divers.
Several studies have been performed recently to investigate the impact of scuba diving on coral reefs, but little is known about the impact of scuba diving on other benthic habitats.
The aim of this study was to compare marine environments frequently visited by scuba divers (Dive zones) to untouched marine environments (Off-limit zones) in Lake Grevelingen, the Netherlands. A total of 512 underwater plots were photographed at eight different dive sites. The dive sites were split up into “dive zones” and “off-limit zones”, both consisting of 32 plots at four different depths.
Six marine phyla (Mollusca, Tunicata, Macroalgae, Porifera, Cnidaria, Echinodermata) were scored present/absent in each underwater plot. When the phylum was scored present, the abundance was quantified using a Coral Point Count. A linear model of the relative abundance of the marine phyla was used to detect differences between the “dive zones” and the “off-limit” zones.
Results came to the conclusion that relative abundance of Mollusca was significantly higher in the dive zones. Although the robustness of bivalves may explain why they are not declining in abundance due to the impact of scuba diving, it does not explain why bivalves are less abundant in the “off-limit zones” in Lake Grevelingen. No significant differences in relative abundance of Tunicata, Macroalgae, Porifera, Cnidaria and Echinodermata were found between the aforementioned zones, thus can be concluded that scuba diving has no impact on these phyla in Lake Grevelingen.
Increasing the awareness of the impact of scuba diving has on marine life is important in order to maintain ecosystem processes and avoid loss of marine species. This can aid in preserving and conserving the precious marine environment as well as the economic and recreational values which scuba diving provides.
Julia van Beinum