Grants and Contributions:

Grant or Award spanning more than one fiscal year. (2017-2018 to 2018-2019)

Dissolved organic matter (DOM) represents the mixture of decomposing plant and soil matter that washes into lakes and streams, with the organic products generated by aquatic animals themselves. Recent findings suggest that DOM could have important direct effects on the biology of aquatic animals, but to date there is little understanding of these effects and how they are mediated. The current program seeks to develop an advanced understanding of the direct biological functions of DOM, through research in four distinct, but overlapping, areas.

One research focus will determine whether nutrients, such as amino acids, which are important components of DOM, contribute to the growth and development of early life-stages of fish. Larval fish undergo periods where they have no functional gut and no yolk supplying nutrients. It is hypothesised that small nutrient molecules could be absorbed by the skin and support fish health. This would offer a way of increasing the productivity and survival of fish in aquaculture, and could result in cheaper and more effective feeds. A second research focus asks a similar question, but in aquatic invertebrates, such as insect larvae. Knowledge of DOM’s role in supporting insect nutrition will offer significant insight into factors that influence seasonal variation in biting insects, such as black flies and mosquitoes, important vectors of disease and irritation.

The third focus is to understand the role of DOM in the evolution of a true digestive system in vertebrate animals. In aquatic biota there is a transition from absorbing nutrients (DOM) directly from the water, as in many marine invertebrates, to the true gut of species such as fish. This research aims to determine the biological factors that are responsible for this transition, by examining the absorptive and barrier properties of the skin, along with digestive structure and function in an array of invertebrate and early vertebrate animals. This work will provide fundamental knowledge of the interplay between physiological phenomena, and how various animal groups have balanced these to provide the necessities of life.

The final research focus seeks to match the chemistry of DOM's to their biological effects on aquatic animals. This work builds on growing recognition that DOM can directly cause stress in animals. However, to date, why certain pathways are affected, and why these effects are restricted to certain DOMs is not well understood. Given that most researchers ignore the possible roles of DOM on aquatic animal health, this work will increase awareness of DOM actions on biota, and will represent the first steps towards a model that will allow prediction of these effects based on the unique composition of DOM in a specific waterway.