Effects of water temperature and sediment disturbance on contaminant uptake from sediment to algae

Abstract

To examine the uptake of metals under varying conditions of temperature and disturbance from historically contaminated sediment (collected at Lytham St. Anne’s, 53o43’58”N, 2o57’37”W) to a natural microphytobenthic community a study was conducted using an intertidal mesocosm. The study ran for a total of 231 days (from 16th September 2015 to 3rd May 2016) under three water temperatures (ambient, plus 1.5oC and plus 4.0oC) with sampling of algae and water at 10 intervals. Biomass on the sediment surface was monitored using Normalised Difference Vegetation Index (NDVI) as a proxy. Diatoms were found to have a higher uptake of the metals analysed (except tin) than other types of algae (filamentous and sheet macroalgae), confirming their importance as a study organism with respect to metal uptake and potential mobilisation through the food chain. Sediment disturbance was shown to increase metal uptake from the sediment to algae, which is of concern due to predicted increases in storminess, as a consequence of climate change, which is likely to increase sediment disturbance and therefore future metal uptake to algae. There were indications of an antagonistic effect of temperature on sediment disturbance. Whilst disturbance increased uptake of metals to algae, increasing temperatures reduced this for some metals.