Harmful algal blooms

Harmful algal blooms (HAB) have been investigated from several different perspectives, including, but not limited to, their taxonomy, physiology, and the life cycles of their component organisms.

Diversidad del fitoplanctonDiversity of phytoplankton

Species are the natural functional units of life and their appropriate identification is essential in assessments of phytoplankton diversity, in order to gain insight into the ecology, biogeography, and speciation mechanisms of these organisms. Estimates of phytoplankton diversity are still based primarily on morphological features but in recent years the incorporation of molecular biology into ecological studies has provided crucial information on the genetic structure of species and especially on those populations of marine organisms that show little morphological diversity. Moreover, cryptic species are known to be present in phytoplankton and while they are difficult or impossible to determine morphologically they can be detected based on their physiology, life-cycle traits, or habitat. This has numerous practical implications, for example, in the genera Alexandrium and Pseudo-nitzschia, in which some species are toxic and others not.

Spatio-temporal distribution of species: time series and biogeography

Our group studies species distribution with respect to environmental conditions in order to understand the processes that lead to bloom formation and to their eventual disappearance, as well as those that can alter bloom dynamics and properties.

Distribución espacio-temporal de las especies: biogeografia y series temporales

Knowledge of the geographical distribution of bloom-forming species and of the long-term fluctuations in their community composition is crucial to identifying whether bloom events are new or recurrent and whether they are likely to expand globally. Similarly, a species’ biogeography reveals whether it has been recently introduced and, if so, its potential origins.

We have defined the spatio-temporal distribution of the most problematic species of the Mediterranean Sea. This is a first but significant step in our efforts to understand the phenomena underlying bloom formation and to elucidate the factors that favor phytoplankton proliferation.

Ciclos de vida de las especiesLife cycles of bloom-forming species

The initiation and subsequent development of a phytoplankton proliferation requires an inoculum of cells. This can originate from different sources and may involve different states of the phytoplankton life cycle. For example, resting cysts, i.e., those persisting in sediments for prolonged periods, are often considered as the starting population that ultimately gives rise to HABs. Both the latency period and environmental parameters modulate the germination of these cysts and thereby determine when the bloom occurs.

Our priority in the investigation of phytoplankton biology is to identify the mobile and resting phases of the respective species, the factors that control the transitions between them, and those that define their life cycles.

Estrategias adaptativas y tasas biológicas de microalgas nocivasAdaptive strategies and biological rates of harmful microalgae

Each phytoplankton species is adapted for life in its particular environment. Moreover, these adaptations may confer a distinct survival advantage over other species in the community. An understanding of the relationship between a species and its environment as well as the phytoplankton community requires studies of the growth, mortality, and life strategies of that species and of its physical and chemical interactions with its surroundings. Both the limits of tolerance and the specific phenotypic characteristics (growth, assimilation of nutrients, vertical migration) of a phytoplankton species contribute to defining its environmental niche and the nature of its relationships with biological components of the ecosystem (competition commensalism, parasitism), which in turn may force alterations in its behavior patterns or the patterns of neighboring species. Our studies are based on in situ measurements of growth and mortality rates and of the incorporation of inorganic and organic nutrients. We also examine the relationship of the target harmful species with its accompanying community, including the roles played by consumers, parasitism, and bacterioplankton.