Marine Protected Areas (MPAs) are recognized by international government bodies and legal diplomas (eg Convention of Biological Diversity, Marine Strategy Framework Directive, OSPAR Convention) as fundamental tools for the management of the marine environment, because they provide a buffer against acute and diffuse environmental disturbances. The establishment and management of effective networks of MPAs is however hindered by the paucity of the data available for scientists and managers on fundamental aspects of the dynamics of marine populations. This paucity of data is basically rooted on the fact that most marine species have a bi-phasic life cycle, where a small planktonic larva precedes a benthic adult. Given that the small larvae are dispersed by marine currents in a medium with diffuse boundaries, local reproduction is decoupled from local recruitment and subpopulations of marine species are distributed over habitat patches that differ in quality, population growth rate and connectivity with the remaining subpopulations. Empirical and theoretical studies indicate that persistence of populations such as these depends on two basic mechanisms: i) self-persistence of local populations and ii) persistence that depends on connectivity among several local populations. Connectivity among subpopulations of marine species, mediated by larval flux, is therefore an emergent and critical property of these systems and a key consideration in the design and placement of MPAs.

How to assess connectivity of populations and monitor dispersal in planktonic larvae is one of the most hotly debated topics in contemporary marine biology. The small size of the larvae and the physical conditions under which dispersal takes place make direct monitoring effectively impossible. Researchers have, therefore, been obliged to resort to indirect estimates of dispersal. As of yet, there is still no single methodology that can address the demographic, genetic, and evolutionary consequences of dispersal in marine populations. This has hampered our understanding of oceanic dispersal processes, an understanding that is crucial if we want to conserve and exploit marine resources sustainably. In an attempt to solve this scientific conundrum, there has been a growing consensus on the need to use multiple tools to assess the typical dispersal scales and pathways of marine organisms, in order to support the management of marine biodiversity.

The core objective of LarvalSources is to estimate connectivity between two Portuguese MPAs, the Reserva Natural das Berlengas and the Parque Natural da Arrábida, and among these and the remaining coast, in order to obtain basic information to assess the factors that may influence their persistence and ecological performance. We will use two rocky reef species with contrasting life-history traits, a blennid fish and a mussel, and two complimentary techniques to assess connectivity, elemental fingerprinting and biophysical modeling, which are two of the most promising methods to address this problem. Trace elements from the natal environment incorporated in the fish otolith and mussel shell primordia will be sampled with Laser Ablation techniques and detected with Inductively Coupled Plasma Mass Spectrometry. Atlases of natal signatures based on these measures will form the basis for the assignment of recruits to their respective natal populations and the construction of empirical connectivity matrices. Predicted connectivity matrices will be estimated by a numerical model of circulation based on the Regional Ocean Modeling System, coupled to an individual-based model simulating larval biology.

If predicted and observed matrices match, then an understanding of the spatial scales of connectivity, the mechanisms underlying larval dispersal and the strength of connectivity pathways will be obtained. If they do not match, then the Individual Based Models will be refined in order to obtain a better description of observed connectivity. In order to account for temporal variability of dispersal driven by the variability of ocean currents, this study will be performed in two different years. As a corollary to this study the results on connectivity will be used in a demonstrative analysis of the role of the two MPAs on the persistence of the populations and of yield of the mussel artisanal fishery.

The research team of LarvalSources has been studying the factors controlling larval dispersal and supply to coastal populations of benthic organisms, using intensive programmes of field observations and numerical modeling of circulation and larval biology. By coupling this experience with our knowledge on the use of geochemical markers we believe we are in a good position to address the integrative use of these promising tools to assess the ecological performance of the Portuguese network of marine protected areas.   

CESAM members on this project

Henrique Queiroga
Principal Investigator

Jesús M. Pedreira Dubert
Investigador

Maria de Fátima Lopes Alves
Researcher

Researcher

Ricardo Jorge Guerra Calado
Researcher