Marine Biogeography and Ecosystems of the Caribbean

Marine Biogeography & Environmental Factors

Caribbean Basin part of Tropical biogeographical region

Affected by freshwater influx from South American Rivers, Gulfstream, Tropic of Cancer and Central and South America

Open waters have less nutrients

Currents, tidal waves and shallow waters allow species mixing but are vulnerable to pollution

Marine Ecosystems

Coastal ecosystems:

1) Mangroves

2) Coral Reefs

3) Seagrasses

4) Estuaries

5) Beaches

6) Rocky shores

Open ocean zones:

1) Epipelagic (0-200 m) sunlit, high O2 and 90% of marine life

2) Mesopelagic (200-1000 m)

3) Bathypelagic (1000-4000 m)

4) Abyssal (>4000 m)

Coral Reefs

Built by Cnidaria (hard corals)

Nematocysts used to catch prey

Require zooxanthellae (symbiotic algae)

Reproduce asexually to form colonies (polyps)

Found near islands, need light and warm waters

Reef types: Barrier, Lagoon and Fringing

Coral reef biodiversity & Bleaching

Scleractinian corals: 60 species

Reef fish: 800 species

- Neon gobies: rapid radiation (one lineage diversifies into new forms) due to isolation by Panama Isthmus

Coral bleaching: breakdown of coral-algae symbiosis due to stress

- Causes: High temp/light, pollution, disease and low salinity/temp

Leads to loss of color and death

Reef Conservation and Food Webs

Overfishing --> Macroalgae overgrowth --> Coral decline

Sea urchin (Diadema antillarum) mass mortality worsened coral decline

Return of urchins in Jamaican reefs saw coral recovery

Seagrasses

Marine angiosperms in family Alismatales

Must:

- Be fully submerged

- Be rooted with flowering reproduction

- Tolerate salt and compete in marine environments

Caribbean Seagrasses

10 species, 3 dominants:

Thalassia testudinum (Turtle Grass is most dominant)

Syringodium filiforme

Halodule wrightii

Reproduce asexually and sexually

Store vast amounts of carbon in soil

Require: Clear water, stable salinity/nutrients, moderate currents

Threats

Water pollution (nutrients, sedimentation)

Coastal development (dredging, filling)

Overgrazing

Invasive species: Halophila stipulacea

Algae

Not monophyletic: Includes micro/macroalgae

(dinoflagellates, red, brown, green)

Red tide: Dinoflagellates → toxic to marine life

Caribbean macroalgae:

Red, Green, Brown

Sargassum blooms since 2011 due to nutrients + climate change

Sea turtles

6 out of 7 sea turtle species found in Caribbean

Migrate long distances and return to beaches to rest

Migration by magnetic navigation and chemical cues

Nesting affected by temp (Sex determination)

Marine Mammals

Manatees (Order Sirenia)

West Indian Manatee: Widespread in Caribbean & Florida

Threats: Boats, nets, habitat loss, red tides

Vulnerable to cold, low metabolism, reproduce

slowly

Caribbean Monk Seal (Extinct)

Overhunted for blubber

Cetaceans

Mysticeti (Baleen Whales)

6 species in Caribbean

Filter-feeders, solitary, long-distance migrations

Humpback whales migrate from North Atlantic to Caribbean to breed

Odontoceti (Toothed Whales)

21 species in Caribbean

Families: Delphinidae, Physeteridae (sperm whale), Kogiidae, Ziphiidae

Use echolocation, live in social groups

Sperm whales: Loudest animals, deep divers, complex social structures