Assessing anthropogenic stressor impacts on intertidal microphytobenthos

Description

The microphytobenthos (MPB) are an assemblage of microscopic autotrophs and mixotrophs which inhabit the surface few millimetres of sedimentary habitats and are the main primary producers in unvegetated intertidal flats. MPB are ecosystem engineers and, through the exudation of organic products and the formation of a biofilm, can hinder the erosion of sediment. Exposed not only to tidally driven changes in physical conditions, MPB communities may experience anthropogenic sources of stress originating in marine, terrestrial, and freshwater environments, including a range of pollutants. However, our understanding of the effects of many of these stressors on MPB communities and their associated ecological processes –individually and cumulatively – is still limited. Further, disentangling stressor effects from environmental context without minimising experimental realism is challenging. Experiments were carried out to investigate the response of MPB to multiple anthropogenic stressor exposure (herbicide and TiO2 nanoparticles) in both laboratory mesocosms and the field (Eden Estuary, Scotland), and framed with statistical power analysis based on prior sampling of intertidal MPB in UK estuaries. Laboratory experiments assessed stressor impacts on MPB in the absence of confounding factors such as initial macrofaunal and MPB communities. Field experiments using these stressors were carried out over a limited surface area in a series of patches and monitored non-invasively using pulse-amplitude modulation and field spectroscopy for a week before destructive sampling techniques were applied, to assess sediment stability, and chlorophyll and colloidal carbohydrate content. Results from both sets of experiments provided evidence for detrimental impacts of herbicide exposure at levels relevant to application dosages, with a neutral or mitigating effect of TiO2 nanoparticles. Laboratory experiments were shown to have value in both assessing individual and combined stressor effects, and in determining field replication requirements in conjunction with power analysis.

Period	5 Sept 2022
Held at	Estuarine and Coastal Sciences Association, United Kingdom