Interactions of light and organic matter under contrasting resource simulated environments: the importance of clonal traits in the seagrass Zostera noltii

Abstract

Light reduction in the water column and enhanced organic matter (OM) load into the sediments are two main consequences of eutrophication in marine coastal areas. This study addresses the combined effects of light, OM, and clonal traits in the seagrass Zostera noltii. Large Z. noltii plants were grown in sand with or without the addition of OM and under two light levels (high light and low light). Whereas some complete plant replicates were grown under homogeneous light and/or OM conditions, other replicates were grown under contrasting light and/or OM levels between the apical and the distal parts of the same plant. The three-way factorial design (light, OM load, and apex position) allowed us to determine the harmful effect of light reduction and OM enrichment on the growth, photosynthetic performance, and biochemical composition of Z. noltii. The addition of OM to the sediment promoted a decrease, or even an inhibition, in net plant growth regardless of the light level when the whole plants were grown under homogeneous light conditions. However, the results differed when plants were grown under contrasting light and/or OM conditions between apical and distal parts. In this case, the harmful effect of OM load was alleviated when apical parts were grown under high light conditions. OM loads also negatively affected the photosynthetic performance, evaluated as leaf fluorescence. The results indicate the importance of clonal traits in the response of Z. noltii growth to light conditions and OM enrichment.

Elevated ammonium concentrations and low light form a dangerous synergy for eelgrass Zostera marina

“…High nutrient availability affects seagrasses in several ways. The major effects are indirectly caused by the proliferation of phytoplankton, epiphytic microalgae and fast-growing drifting macroalgae promoting light attenuation (Sand-Jensen & Borum 1991, Hernández et al 1997, Valiela et al 1997, Hauxwell et al 2001, McGlathery 2001, Bryars et al 2011, Lyons et al 2012 or increasing the sedi-ment organic matter load, which may reduce oxygen levels and increase the risk of anoxia (Greve et al 2003) and sulfide intrusion into the plants (Holmer & Bondgaard 2001, Borum et al 2005, Pérez et al 2007, Olivé et al 2009). Furthermore, there may be a direct effect of high nutrient availability on seagrasses since exposure to high concentrations of NH 4 + can be toxic to higher plants (e.g.…”

Phytoremediation of Eutrophic Waters

“…(El-Shafai et al 2007 ;Ansari and Khan 2009a ;Lu et al 2010 ). Light reduction in the water column and enhanced organic matter load into the sediments are two main consequences of eutrophication (Olive et al 2009 ). Temperature is important environmental factor directly related with the functioning of an aquatic ecosystem (Ansari et al 2011b ).…”

Seasonal dynamics in the trophic status of water, floral and faunal density along some selected coastal areas of the Red Sea, Tabuk, Saudi Arabia

“…Increase in phytoplankton species, water temperature and frequent decomposition of dead planktons and other organic matter results in depletion of oxygen level (Calliaria et al 2005). Light reduction in the water column and enhanced organic matter (OM) load into the sediments are two main consequences of eutrophication in marine coastal areas (Olive et al 2009). In eutrophicated coastal waters seagrass decline was found associated with light intensity (Burkholder et al 2007).…”