Distribution of marine algae along the coastline of the Maltese islands in relation to environmental factors

Abstract

The supralittoral zones of Daħlet Qorrot, Dwejra, Anchor Bay, Gnejna Bay, Manoel Island and Pretty Bay along the Maltese and Gozitan shorelines were chosen in order to identify the relationship between the distribution of macro-algae and environmental factors. Abiotic and biotic factors were taken into account. These consisted of sea temperature, pH, dissolved oxygen, orientation, open/closed sea, light intensity, wind force, pollution, accessibility, distance from wading depth to shoreline, slope of shoreline, length of shoreline, turbidity, chlorophyll a, Phosphates, and Nitrates. All these factors contributed to outline the parameters for both the summer 2011 and winter 2012 seasons. The first 13 physical factors could be recorded in situ, whereas for the latter four, water samples were collected from each site and further lab analysis were carried out in order to obtain the relevant results. The macro-algal species collected from the study sites during the summer season were 18, having Jania rubens and Ulva sp. as the most abundant species all along the whole season. Jania rubens and Ulva sp. were dominant in almost all the points of the study sites. While only 13 macro-algae species were identified during the winter season, Enteromorpha being the only macro-algal specie dominant; this was the only macro-algal species present in almost all the points of the study sites. Sea temperatures and anthropogenic disturbances increased in summer, although the levels of chlorophyll a increased in winter. The turbidity readings were correlated with wind forces, while pH levels remained relatively constant throughout the whole study. Phosphates and Nitrates tests gave opposing results; one decreased when the other increased. GIS mapping was used for each study site, in orde Along with this, graphs were also incorporated in order to contrast variants with each other and analyse their relationship. An abundance of macro-algae species was present during the summer season, whereas the indicative factors fluctuated according to the weather, environmental and anthropogenic disturbances present at the time. Apart from anthropogenic influences, it was the temperature variation associated with seasonal change that exerted most influence of the difference between algal assemblages.