oa Chlorophyll and phaeo-pigments in mangrove sediments in an arid environment in the Arabian Gulf, east coast of Qatar

Mangroves are one of the most important ecosystems in Qatar, Arabian Gulf. They support complex, yet poorly studied food chain. Microphytobenthos are known to have better nutritional values and more palatable than mangrove leaves. There are very few studies on the standing stock of the sediment microphytobenthos in the mangroves of the Arabian Gulf. It is important to quantify the micophytobenthos in the mangrove ecosystem in order to understand their role in the food web and in the carbon cycle. Sediments’ chlorophyll and phaeo-pigments were measured in three locations representing three different ecosystems (natural mangrove, planted mangrove, and sand flat), in the east coast of Qatar. Biweekly samples were collected in the period between Fall 2013 and Spring of 2014. The present study used the chlorophyll concentration as a proxy to quantify the biomass of the microphytobenthos in sediments in the three ecosystems selected. Chlorophyll A, B, C, and phaeopigments were analyzed using the method of Lorenzen and Jeffery (1980). The study compared the biomass of benthic chlorophyll in intertidal and subtidal sediments in three habitats; natural mangrove (Dakhira), planted mangrove (Semisma) as well as a sand flat (the pearl). Chlorophyll-A concentrations were significantly different between mangrove habitats and sand flat (P<0.05). The average concentrations of sediment chlorophyll in natural mangrove was about five times (4.7 μg g−1) compared to that of non-mangrove sand flat (0.98 μg g−1). Chlorophyll B was most abundant in Al-Dakhira mangrove with average concentration of 2.5 μg g−1 that was significantly different from the concentrations determined in the sand flat (P>0.05). High concentrations of phaeopigments were found in Al-Dakhira (6-35 μg g−1 ) indicating higher grazing and biodegradation activities compared with the sand flat (2-11 μg g−1). Natural and planted mangrove ecosystem constituted higher sediment microphytobenthic biomass than sandy beach as hypothesized.