HABs in Stratified Systems
The GEOHAB Core Research Project on Harmful Algal Blooms (HABs) in Stratified Environments directly addresses the goal of GEOHAB of improved prediction of HABs by determining the ecological and oceanographic mechanisms underlying their population dynamics, integrating biological, chemical, and physical studies supported by enhanced observation and modelling techniques. The overall objective is to determine the factors underlying the development of communities related to HABs in sub-surface micro-layers and the real-time dispersion of these microlayers as a function of turbulent and advective regimes.
The temporal and spatial scales of thin layers (intermittent and less than 1 m thickness) in a variety of hydrodynamical regimes pose problems for sampling and modelling of harmful bloom populations. Coupling physical effects (turbulence, shear, and advection) and biological behaviour (migration, physiological adaptation) holds the key to understanding vertical distributions, bloom dynamics, and patterns of toxicity. Some of these physical processes are not yet defined at the proper scale, yet may be crucial in the formation of harmful blooms. It is in these areas where our knowledge is weakest.
Models have thus far been restricted by insufficient ability to gauge the interactions between the biology of algal taxa and underlying physical processes. As an example of chemically mediated interactions that may be very important in highly stratified systems, certain harmful species can produce exotoxins that may have an allelopathic effect on competitors for substrate, or even inhibit grazers. From the biological perspective, the relative importance of biological processes occurring within or at the interface of thin layers, such as species-specific adaptations for heterotrophy and the role of the microbial food web, are also poorly understood. Sharing of expertise and specifically designed instrumentation will enable testing of common research hypotheses in different geographical locations and across various hydrodynamical regimes.
The Science Plan for the Core Research Project was launched October 2008.