Development Of A Protocol For Culturing And Maintaining Seagrass, Halodule Uninervis, Under Laboratory Conditions And Its Application To Determine Impacts Of Light On Seagrass Growth

Abstract

Seagrass meadows are an important component of the marine ecosystem as they not only contribute nutrients and organic carbon to the nutrient cycle, but also, provide food, habitat and nursery grounds for a plethora of marine vertebrate and invertebrate species. Several environmental and anthropogenic factors have caused a major decline in their population worldwide. In the Gulf region, the Seagrass is extensively found in the coastal waters and like other marine species, are facing extreme natural stressors, like high temperature and salinity. Additionally, dredging, reclamation, increased eutrophication due to an increase in domestic and industrial discharges as a result of rapid ongoing urban development, such as in Qatar, may impose a threat on the health of the seagrass. These can increase the amount of suspended particles in water and thereby reduce the amount of light reaching the seagrass population. Consequently, their photosynthetic activity can decline and may reach very low levels affecting the rest of the food web that are connected to the seagrass population for either food or habitat. Despite the immense importance of the seagrass neither much is known about its ecology nor about its association and dependence on the abiotic.

factors. This study was designed to investigate the possibility of maintaining indigenous seagrass species under laboratory conditions so as to be able to understand its ecology and requirements for providing a sustainable population. Furthermore, this study investigated the impact of three light intensities on the health of seagrass held at a constant temperature of 22ºC for about two months. Pulse Amplitude Modulated (PAM) fluorometry was used to assess the maximal quantum yield (YII) which is the photosynthetic response of seagrass to various light intensities. The study demonstrated that it is possible to maintain and achieve growth in seagrass population under controlled laboratory conditions. The PAM measurements showed that the growth of seagrass is dependent on the amount of light received. A total lack of light led to a 66% decline in YII while a light at 227 PAR (μmolm-2s-1) enabled the seagrass to maintain its photosynthetic ability as seen in the field. A further increase in light (452 PAR) increased the photosynthetic function only slightly.