Quantification of Nutrient Related Ecosystem Functions in Zostera Marina Meadows - A Review

Abstract Populations of seagrasses such as eelgrass ( Zostera marina ) have been declining worldwide within the last century. This loss has partly been attributed to mechanisms associated with increases in nutrient loading from anthropogenic sources. Furthermore, the systems are kept in a degraded state through feedback mechanisms caused by loss of the eelgrass habitat’s nutrient-related ecosystem functions. In this article, we reviewed the available published data and methods used for the quantification of nutrient-related ecosystem functions. We focused on three pathways of nutrient retention/export: (1) Assimilation in the eelgrass biomass, (2) nutrient burial and sedimentary stocks, and (3) microbially driven nutrient cycling. We conceptualized the mechanisms driving these ecosystem functions and evaluated the current methods’ applicability regarding the quantification of nutrient budgets. We found that studies often lack data from a comparable control site, and the ecosystem function could therefore not be derived. This was evident in studies of sediment stocks and microbial cycling, which often only included data from eelgrass. Standing biomass of eelgrass was commonly measured, but few considered the production and turnover of biomass as an annual cycle. Studies relating to microbial nitrogen cycling were the most abundant in the literature, but they often lacked simultaneous measurements of N-fixation and denitrification and thus did not allow for a net N 2 -flux calculation. We concluded that there is need for studies that consider the underlying mechanisms driving the ecosystem functions across all topics, and that restoration sites are a great opportunity to investigate the development of the ecosystem functions that seagrass habitats facilitate.