Curso de Lagunas Costeras Alice Newton Universidad de Algarve, Portugal Universidad EAFIT, Abril 8-23, 2008

Conclusion: Land-Ocean Interactions and Coastal Lagoons Vulnerability and risk, coastal erosion, sea-level change, storms, tsunamis Coastal development and change in agriculture River-basins and human dimensions, changes in sediment supply, coastal engineering Biogeochemical budgets, changes in nutrient supply Towards system sustainability and resource management issues

Why do populations settle around Coastal Lagoons? ~ Attractive for human settlement ~ Marine but sheltered waters Transport, harbour facilities ~ Often associated freshwater inputs from watershed ~ Productive fisheries and bivalve harvests ~ Salt-extraction ~ Recently: tourism and leisure industry Phoenician city of Carthage: Lac de Tunis Venice in the Middle ages, Renaissance, Present crisis

How do Human modify lagoons? ~ Physical modifications ~ Chemical modifications ~ Biological modifications ~ Social modifications

Sediment dynamics Many of our engineering “feats” interfere with sediment dynamics. Sediment dynamics and turbidity can affect important biological communities such as seagrass.

Chemical modifications Are coastal lagoons drains? ~ Geomorphologically? ~ Yes they are.

But should they be sewers? No! These are point sources that we can resolve by the building of extensive sewer systems and sewage treatment plants… Lagoons perform denitrification NATURALLY …

What about diffuse pollution? ~ Much more difficult to address ~ Agricultural sources are main input ~ Eutrophication and all the cascade of direct and indirect effects this implies may be the result. ~ Global impact of nutrients on coastal lagoons.

Biological modifications? ~ Overfishing ~ Aquaculture ~ Introduction of exotic species ~ Ecological imbalances and the proliferation of nuisance species ~ Impact on the foodweb and alterations in trophic relationships

Ecological imbalances and the proliferation of nuisance species Type of problem caused by macrophyte blooms in many coastal lagoons

Impact on the food web ~ Ecological shifts in primary producers have wide ranging consequences in the food web ~ Lagoons often act as a breeding or nursery for important species.

Social changes ~ Modifications in the way humans use lagoons e.g. Tidal mills (no longer in use) Tidal dams renewable energy Salt pans converted to aquaculture ~ Increased environmental awareness Attach value to environmental quality Value of tourist, leisure industry...

The 21 st Centuary and Coastal lagoons research ~ Use models to optimize monitoring ~ Better understanding of atmosphere and land impacts on the coastal ecosystems ~ Better understanding of ecosystem function and biodiversity of coastal lagoons ~ Link ecological and socio-economical studies ~ Attach real value to ecosystem services, such as denitrification ~ Raise environmental awareness through education and public information

What is the magnitude and speed of change on coastal lagoons that is being inflicted by change to biogeochemical cycles; can the systems recover and are the result within “acceptable” limits? Can we identify what makes systems sensitive/robust? Can we assess of the implications of habitat, ecosystem services and land loss on regional and global biogeochemical cycles? How close do these losses take the system to thresholds of significant change in regional biogeochemical functions, thus affecting these natural goods and services? Can we identify the potential role of different assemblages and habitats in sustaining the integrity of coastal lagoons and Earth processes? Can we delineate the balance between increasing and decreasing sediment loads to the coastal zone due to man and/or climate change, and its impact on coastal evolution especially on wetlands and estuaries? Information gaps that still need addressing