Abstract
The transport of dissolved organic matter (DOM) to coastal waters in Europe and the USA has increased during the last decades. This DOM, originating from terrestrial ecosystems is affecting the marine ecosystems in several ways. DOM has for example been shown to be an important factor facilitating growth of Harmful Algal Bloom (HAB) phytoplankton species. It is suggested that it is the nitrogen in the DOM that is beneficial for the HAB-forming phytoplankton, and uptake of smaller molecules such as amino acids containing nitrogen has been shown to take place. However, virtually nothing is known about the possibility that HAB-species utilizes larger molecules such as proteins or humic substances for growth. A large part of the DOM entering coastal waters are high molecular, and preliminary experiments suggests that there can be an active uptake of these large molecules by phytoplankton. We propose to study the utilization of macromolecular DOM by several potentially harmful phytoplankton species. Our main objective is to investigate the possibility of these species to utilize large nitrogenous molecules directly, but also to reveal the mechanism behind the direct uptake. In addition, we will evaluate the competitive advantage that comes with direct uptake of large molecules containing nitrogen. If this is a common trait among HAB-forming phytoplankton, then this has implications for a further increase in HAB blooms when the input of HMW-DOM to coastal waters is increasing.
Sweden