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Seagrass lecture Seagrass lecture Presentation Transcript

  • Coastal communities: Seagrass beds
    Dr. Loretta Roberson, UPR-RRP and Institute of Neurobiology
  • OUTLINE
    What is seagrass?
    Associated flora and fauna
    Seagrass ecosystem function
    Habitat connectivity
    Disturbances and threats
  • What is seagrass?
  • What is seagrass?
    Leaf
    Rhizome
    Root
    Sheath
  • What is seagrass?
    True flowering plant (angiosperms)
    Monocots (lily, corn, rice)
    Not a true grass
    Wholly submerged in salt or brackish water
    Can reproduce sexually and asexually
    developed a submarine pollination mechanism
    can produce large, old clones
    (600 m2 and >1,000 years old)
  • What is seagrass?
    Aerenchyma
    specialized parenchyma with regularly arranged air spaces (gas exchange, buoyancy)
    Chloroplasts in the leaf epidermis
    Require high light levels
    25% of incident radiation (compared to 1% in other plants)
    supports large amount of nonphotosynthetic tissue
    must provide oxygen to roots and rhizomes
    (toxic sulfide sediments)
  • What is seagrass?
    59 species worldwide in 12 genera
    Abundant in Australia, Alaska, S. Europe, India, E. Africa, SE Asia, Caribbean, Gulf of Mexico
    7 species found in Caribbean:
    Thalassia, Syringodium, Halodule, Ruppia, Halophila engelmanni, H. decipiens, and H. baillonii
  • What is seagrass?
    7 species found in Caribbean:
    Thalassia, Syringodium, Halodule, Ruppia, Halophilaengelmanni, H. decipiens, and H. baillonii
    Thalassia
    Syringodium
  • World Seagrass Distribution
    From: World Atlas of Seagrasses 2003
    Coral distribution
  • World Seagrass Distribution
    Florida
    Gulf of Alaska
  • Factors affecting distribution
    Physiology
    Temperature
    Salinity
    Waves
    Currents
    Depth
    Substrate
    Day length
    Photosynthesis
    Light
    Nutrients
    Epiphytes
    Disease
  • General Habitat Characteristics
    Shallow, soft bottom
    Clear water
    Protected from wave action
    Monospecific or mixed stands
    Patchy
  • Associated flora and fauna
  • Associated flora and fauna
    Bacteria
    Fungi
    Diatoms
    Algae (green, red, brown)
    Protozoa (slime mold, forams)
    Sponges
    Cnidarians (corals)
    Polychaetes
    Ribbon worms
    Sipunculid worms
    Flatworms
    Crustaceans (shrimp, lobster)
    Bivalves (oysters, scallops)
    Gastropods (Conus, Strombus)
    Cephalopods (squid, cuttlefish)
    Bryozoans
    Echinoderms (sea cucumbers)
    Tunicates
    Fish (snapper, sea horses)
    Reptiles (green turtles)
    Birds (Brant geese)
    Mammals (dugong, manatee)
  • Functions of seagrass – An ecosystem perspective
    Primary production
    Canopy structure
    Below-ground structure
    Wave and current energy damping
    Nutrient, contaminant and sediment filtration and trapping
    Nutrient regeneration and recycling
    Epiphyte and epifaunal substratum
  • Primary production – Photosynthetic organisms
    Cyanobacteria
    Diatoms and Coccolithophores
    Algae – includes zooxanthellae
    Plants – seagrass
  • Primary Production
    ·  primary production = rate of photosynthesis or chemosynthesis
    ·  utilize sunlight or chemical nutrients as a source of energy (autotrophy)
    ·  the lowest level of the food chain
    Primary producers serve as the basis
    for nearly all life in the ocean
  • Factors Affecting Primary Productivity
    Light
    Nutrients
    Hydrographicconditions
    Currents
    Upwelling
    Vertical mixing
  • Estimates of primary production
    Pelagic zone = 50-600
    Grasslands = 2,400
    Tropical forests = 5,000
    Mangroves = 2,700
    Coral reefs = 1,200-8,000
    Seagrass beds = 800-10,000
    (measured as g C/m2/yr )
  • Ecosystem function – Canopy structure
  • Ecosystem function – Canopy structure
  • Ecosystem function – Below-ground structure
  • Ecosystem function – Epiphyte and epifaunal substratum
  • Ecosystem function – Epiphyte and epifaunal substratum
  • Ecosystem function – Epiphyte and epifaunal substratum
  • Ecosystem function – Wave and current energy damping
  • Ecosystem function – Wave and current energy damping
  • Ecosystem function – Nutrient, contaminant and sediment filtration and trapping
  • Ecosystem function – Nutrient regeneration and recycling
  • Habitat connectivity
  • Habitat connectivity
    N
  • Habitat connectivity
  • Habitat disturbances
    Natural
    Waves
    Hurricanes
    Animal foraging
    Anthropogenic
    Eutrophication
    Sedimentation
    Habitat destruction
    Overfishing
  • Natural disturbances – Waves
  • Natural disturbances – Waves
  • Natural disturbances – Hurricanes
  • Blow outs
  • Natural disturbances – Animal Foraging
  • Natural disturbances – Animal Foraging
  • Natural disturbances – Animal Foraging
  • Natural disturbances – Animal Foraging
  • Natural disturbances – Animal Foraging
  • Anthropogenic disturbances – Eutrophication
    The process by which a body of water becomes enriched in dissolved nutrients that stimulate the growth of aquatic plant life
  • Eutrophication – HABs
    [ Harmful Algal Blooms ]
  • Eutrophication – HABs
  • Anthropogenic disturbances – Sedimentation
  • Anthropogenic disturbances – Sedimentation
  • Anthropogenic disturbances – Urbanization
  • Anthropogenic disturbances – Urbanization
    10 km
    Shading = >1,000 persons/mi2
    From: Planning Commission of Puerto Rico, Office of Land Use
  • Other anthropogenic disturbances -
    Propeller scarring
  • Other anthropogenic disturbances - Harvesting
  • Caulerpa
    Ballast water
    Other anthropogenic disturbances - Invasive species
  • Anthropogenic disturbances – Overfishing
  • Anthropogenic disturbances – Overfishing
    Before Fishing
    After Fishing
    Jackson et al., Science 293, 629 -637 (2001)
  • Jackson et al., Science 293, 629 -637 (2001)
    >3.3 × 107 adult turtles historically  1.1 × 106 50-kg turtles today
  • Current research
    Orth et al. 2006 Bioscience 56(12): 987-996
    More seagrass research!!
  • Current research
    Effects of water quality on seagrass community productivity and biodiversity in NE Puerto Rico
    USGS Water Resources
    Data 2004
  • “Non-impacted” - 7S
    Impacted - LC
    Study sites – Fajardo
  • Biodiversity - Fish
    Impacted
    “Non-Impacted”
  • Biodiversity - Fish
    *
    * From Kopp et al. 2007 Aquatic Botany
  • Conclusions:
    • Nearshore and watershed water quality are poor,
    mainly due to sediment not nutrients
    • More stable communities may protect biodiversity (and vice versa)
    • Higher frequency measurements are needed, especially light
    • Long-term studies are needed (study is ongoing) i.e., SeagrassNet.org
    • Seagrass conservation areas and nearshore water quality management are needed in Puerto Rico!