Experiments to parametrise a growth and nutrient storage model for Agarophyton spp.

Management of eutrophication in estuaries requires modelling tools to gauge the consequences of nutrient loading from land. We conducted laboratory experiments to quantify the growth response of the opportunistic red algae Agarophyton spp. to seawater nutrient (nitrogen and phosphorus) concentrations, salinity, temperature and light. We derived parameters for a Droop kinetics-type model and calculated critical (corresponding to 67% of maximum growth rates) and minimum values of these environmental factors required for growth. We compared our results with long-term time series of water quality data across a large, highly eutrophic estuary in southern New Zealand. Nitrogen availability and salinity were the environmental factors most likely to restrict summertime growth of Agarophyton spp., but nutrient limitation appeared unlikely at all but the most seaward, high salinity sites. When combined with models of estuarine mixing, this work may aid prediction of growth responses of Agarophyton spp. to nutrient loading at an estuary scale.

Automated summary

This study investigated the growth response of red algae to seawater nutrient concentrations, salinity, temperature, and light. Results showed that nitrogen availability and salinity are likely to restrict the summertime growth of the algae. When combined with modeling, the research may aid in predicting growth responses to nutrient loading in estuaries.