Key Questions

Following the Open Science Meeting (OSM) in Chile in 2004,  seven key research questions were identified that were pertinent to the Fjords and Coastal Embayments Core Research Program. These are:

 

Question 1 

Are there definable adaptive strategies that characterize HAB species in confined and semi-confined systems?

 

An ecologically based classification of the different species found in fjords and coastal embayments should be carried out based on their adaptation to the multiple sub-habitats characteristic of such ecosystems. This should be done with consideration of the type of connection that dominates the confined or semi-confined system: oceanic, land or sediment, and depending on morphology, depth and circulation. The functional role of morphological, physiological, behavioural and life-history characteristics, at the cellular level, should be included in this classification of HAB species in coastal embayments.

 

Question 2

What is the importance of life history transitions and cyst distribution in bloom initiation and maintenance – endogenous seed beds versus exogenous introduction?

 

The seeding strategies employed by HAB species within coastal systems should be identified. Transitions between the vegetative cycle and sexual cycle and a cycle involving the formation of short-term temporary cysts, small-sized cells or aggregates (often in response to short-term environmental fluctuations) need to be identified and understood for each study site. Establishment of the sites of HAB initiation and characterisation of environmental influences on the life history stages of HAB species is a priority in developing a predictive capability.

 

Question 3 

How do physical dispersion and aggregation processes within a semi-confined basin affect HAB growth and distribution?

 

The influence of small-scale physical processes on the growth and dispersion of HAB species should be determined. Thin layers of phytoplankton (and often also of their grazers) frequently occur under calm conditions that may be encountered in fjords and coastal embayments. This vertical structure needs to be taken into account for field sampling. Turbulent mixing determines much high-frequency environmental fluctuation and in so doing can control nutrient, irradiance, and phytoplankton patchiness, and is also known to affect plankton growth rates. Varying responses in terms of the succession of species within and between embayment systems will allow inferences of the properties regulating species succession and the development of HABs.

 

Question 4 

What is the relative contribution of nutrient flux and supply ratios to HAB dynamics in eutrophic versus non-eutrophic coastal embayments?

 

The nutritional physiology of target species should be investigated as related to the natural variation in nutrient signals. Although time-series field measurements of nutrient concentrations can provide valuable insight to nutrient dynamics, provided that trans-boundary fluxes are quantified, direct measurements of regeneration and assimilation rates need also to be performed using isotope tracer methodology. These measurements will serve to provide meaningful input to biogeochemical models that can be employed in a predictive manner when coupled with the primary hydrodynamic forcing typical of fjords and coastal embayments.

 

Question 5

What is the importance of spatial scale and retention time in the expression and effects of allelochemicals/toxins in semi-confined systems?

 

The production of allelochemicals – biologically active components eliciting specific responses in target organisms – may be an important mediator of intra- and inter-specific interactions and may play a role in chemical defence of cells. Other hypothetical functions of allelochemicals include a critical role in cell-to-cell communication, involving processes such as sexuality and life history transitions (Wyatt and Jenkinson, 1997), chemotaxis and apoptosis (“programmed cell death”). The role of phycotoxins in chemical defence against predators or algal and bacterial competitors remains largely unresolved, and their function as allelochemicals is increasingly under scrutiny (Cembella, 2003). Concentration of toxigenic cells of a HAB population into a thin layer would facilitate the development of an effective concentration against target organisms, via creation of a “toxic cloud”. In partially enclosed embayments and fjords that can act as retention zones for allelochemical-producing microalgae, the opportunity for enhanced concentration and hence intensified allelochemical activity may be offered via "quorum sensing" as observed in bacterial populations. In any case, a potential disadvantage or “trade-off” associated with the formation and maintenance of HAB populations in thin layers or other retention zones is the problem of auto-inhibition or auto-toxicity resulting from excretion or leakage of the allelochemical into the surrounding medium. At the termination of the bloom, larger quantities of these endogenous metabolites would be released via cell lysis and decay. Nevertheless, it is expected that the deleterious consequences of this bulk release may be more dramatic upon grazers and competitors within the retention zone than upon the producing organisms.

 

Question 6 

How do embayment morphology, bathymetry and hydrodynamic flux affect HAB dynamics?

 

The importance of the morphology, bathymetry and hydrodynamics of coastal embayments and fjords on the dynamics of HABs needs to be determined. The systems under study should be defined with respect to their basic patterns of circulation, stratification, exchange with outside waters and turbulence, and the driving forces of these patterns (such as wind or freshwater inputs) should be identified. These influences are responsible for creating alternating patterns of circulations along the coast which may serve in creating sites favouring bloom initiation, retention, dispersion, etc. Characterisation of these sites will assist in understanding their role in the dynamics of HABs. Observations should be made with reference to both vegetative and resting stages of HAB species.

 

Question 7

Are the effects of anthropogenic activities (e.g. aquaculture) and global climate change on HAB dynamics magnified in enclosed and semi-enclosed embayments?

 

This question can best be addressed by careful local investigation of site-specific consequences of introduction of new aquaculture stock and the risk of anthropogenic transfer of alien species (including those of HABs) into coastal regimes, for example, via ballast water discharge. Ports and harbours are particularly vulnerable and can act to seed HAB events in adjacent confined waters of embayments. Efforts must also be made to determine whether or not climate indicators can be identified as predictors of HAB events in coastal embayments. Research is required to relate the effects of climate change, and associated variation in the predominant physical and chemical forcing mechanisms, on HAB species and communities that typify coastal environments. Action could be taken to accurately define the specific data and samples to take in upcoming years, in order to “optimize” the tools for analysis to be conducted by future generations on the impact climate change may have on HAB events in coastal ecosystems, at a large scale basis. Does the increased reliance on coastal aquaculture for proteins from the sea increase the risk of HAB events? Is grazing on HAB species altered in aquaculture sites due to the presence of farmed organisms or epibenthos fixed on these?