Ecology of seagrasses in northeastern Saudi Arabia one year after the Gulf War oil spill

Abstract

Approximately 1 year after the Gulf War oil spill we examined the distribution, species composition, abundance and productivity of seagrasses in several oil contaminated bays along the northeastern coastline of Saudi Arabia. The most abundant seagrass, Halodule uninervis, grew from the intertidal down to depths of 10 m with a standing crop ranging from 2 to 32 gdw m −2. Specific leaf productivity in a heavily oiled shallow site (1.5 m depth) was 2.2% d −1 and areal production was 0.172 gdw m −2 d −1. Specific productivity was similar to other reported rates for healthy populations of Halodule species but the low areal productivity reflected late winter water temperatures which were between 16 and 19°C. Halophila ovalis was intermediate in abundance followed by Halophila stipulacea. Leaf morphology and indicators of vegetative growth suggested that all three species were healthy, despite the recent history of oiling. Morphometric analyses indicated the seagrasses were experiencing a seasonal transition and initializing a normal growth pattern from lower winter temperatures to spring conditions. All three species grew in monospecific and mixed species meadows. The highest diversity and biomass of vegetation occurred on a mixture of hard and soft substrates where species of brown macroalgae were dominant. Based on these observations we conclude that seagrasses in the northwestern Gulf have not experienced acute or long-term degradation as a direct result of the Gulf War oil spill.