A Recipe for Biodiversity (PDF)

Introduction to South African Biodiversity CAPE RADD MARINE SCIENCE FIELD TRAINING Where on Earth are we?  Cape Town Cape Town is the only city with both warm AND cold beach environments. This contrast across the Cape Peninsula creates large horizontal ocean temperature and prod...

Introduction to South African Biodiversity CAPE RADD MARINE SCIENCE FIELD TRAINING Where on Earth are we?  Cape Town Cape Town is the only city with both warm AND cold beach environments. This contrast across the Cape Peninsula creates large horizontal ocean temperature and productivity gradients. Study Site: South Africa's coastline stretches 3,113km in length (Sink et al. 2012). The extensive coastline is characterised by a few large embayments and notoriously strong wave action (Griffiths et al. 2010). (Cape of Storms) South Africa has the third-highest level of biodiversity of plants and animals in the world! Brazil is ranked first and Indonesia second highest. South Africa, and particularly the W. Cape, is called a ‘biodiversity hotspot’. (South Africa is the only country to contain an entire floral region) No. of species found in South Percentage of earth's Africa species Marine Invertebrates 8,859 8% Marine Algae 800 10% Marine Fish 2,200 15% The recipe for Biodiversity Terrestrial Bioregions 5 Ecoregions of Southern Africa General Biological Patterns from West to East 1. Productivity decline (growth of plankton + seaweed) 2. A decrease in biomass (animal mass per unit area) 3. Increase in diversity (no. of species) Why? The oceans surrounding South Africa can be divided into three coastal regions. They are: A) The Atlantic Ocean off the West Coast, with cold sea temperatures ranging from 9 –15 C. B) The Indian Ocean off the East Coast, with warm sea temperatures ranging from 18 – 27 C. C) = A and B meet and mix along the South Coast with sea temperatures ranging from 16– 20 C. A. B. C. East Coast - Agulhas Current Summer vs Winter Surface Sea temperatures West Coast - Benguela Current West Coast - Benguela Current Southern African coastal Chlorophyll concentration levels Marine life Food Chain Differences between the East and West coasts The West Coast The East Coast Vast numbers (biomass %) but The water is warm, clear and has relatively few species. relatively low levels of nutrients. Pelagic species such as pilchard Marine life on the east coast and anchovy, and benthic species consists of a large diversity of such as hake and kingklip occur in species, most of which occur in enormous numbers and sustain relatively low numbers. major fishing industries The richest rock lobster and The competition for food is strong perlemoen grounds lie on the west and there is a high proportion of and southwest coasts. On rocky predators. shores, limpets occur at densities Many species are brightly unmatched anywhere else in the coloured and have remarkable world. Seals, penguins and other sea adaptations to allow them to survive in a competitive birds such as cormorants and environment where there are gannets are common on the west coast, particularly on offshore many predators. islands where they breed undisturbed by predators. Begs the Question… Why are there fewer fish species in highly nutrient Cape waters?  Why there are fewer fish species in highly nutrient Cape waters hypothesis 1. Indian Ocean is much older than the Atlantic - More time for evolution and diversification of species? 2. Productivity is so high on the west coast that competition is more intense meaning fewer species can coexist? 3. High variability on west coast with upwellings creating large shift in nutrients, temperature and poor O2 level (blooms) Impacts of the currents on the climate (West coast) The cool waters of the Atlantic west coast provide little moisture for the air moving onshore resulting in very dry conditions on land along the coast. (e.g. Namibian desert) In summer conditions are particularly dry because the south easter blows offshore and the land is left hot and dry. At night fog banks develop over the cold sea and bring some moist relief to the coastal vegetation, but inland there are desert or semi-desert conditions. East Coast A much warmer sea allows abundant evaporation (surface slack) and onshore winds bring more rain to the region. This rain results in lush sub-tropical vegetation. However, in the rain shadow behind the mountain ranges lies the dry Karoo region. Government Management 42 MPA zones 5% Coverage MPA Zonation: Permitted activity zone Fishing / kelp extraction / foraging etc. NO TAKE ZONES (5) Varied Marine Habitats  Marine Habitats are distinguished by the type of substrate. The substrate, or base material, is important as it provides a base to which an organism can anchor itself, this is important for those organisms which need to stay in one particular kind of place. 4 Main Habitat Types: 1. Rocky reef and/or shore 2. Sandy beaches and bottoms 3. Kelp Forest Rocky Shore Rocky Reef and Shore Rocky shores and reefs provide a firm fixed substrate for the attachment of plants and animals. The Majority of the dive sites in False Bay are rocky reefs. (Granite boulders) Sandy shores Kelp Forests Kelp forests are found in polar and temperate coastal regions (susceptible to climate change) Commercial uses (fertiliser, beauty products) Main species of Kelp of South African coast: Sea Bamboo (Ecklonia maxima) (12m)  Keystone Species - Offer a source of food and shelter for many fish and invertebrate species (Very Productive!) Kelp is the fastest and largest growing marine brown algae seaweed Open Water (pelagic zone) The Recipe for Biodiversity in South Africa 5 connected Marine Eco Regions and Terrestrial biomes The acting currents on either side of the continent (nutrients upwelling) Relatively good management from Government (MPA’s) 5% Varied & Keystone Habitats