Seagrass lecture

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Coastal communities: Seagrass beds Dr. Loretta Roberson, UPR-RRP and Institute of Neurobiology
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Transcript of Seagrass lecture

  • 1. Coastal communities: Seagrass beds
    Dr. Loretta Roberson, UPR-RRP and Institute of Neurobiology

2. OUTLINE
What is seagrass?
Associated flora and fauna
Seagrass ecosystem function
Habitat connectivity
Disturbances and threats
3. What is seagrass?
4. What is seagrass?
Leaf
Rhizome
Root
Sheath
5. 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)
6. 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)
7. 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
8. What is seagrass?
7 species found in Caribbean:
Thalassia, Syringodium, Halodule, Ruppia, Halophilaengelmanni, H. decipiens, and H. baillonii
Thalassia
Syringodium
9. World Seagrass Distribution
From: World Atlas of Seagrasses 2003
Coral distribution
10. World Seagrass Distribution
Florida
Gulf of Alaska
11. Factors affecting distribution
Physiology
Temperature
Salinity
Waves
Currents
Depth
Substrate
Day length
Photosynthesis
Light
Nutrients
Epiphytes
Disease
12. General Habitat Characteristics
Shallow, soft bottom
Clear water
Protected from wave action
Monospecific or mixed stands
Patchy
13. Associated flora and fauna
14. 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)
15. 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
16. Primary production Photosynthetic organisms
Cyanobacteria
Diatoms and Coccolithophores
Algae includes zooxanthellae
Plants seagrass
17. 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
18. Factors Affecting Primary Productivity
Light
Nutrients
Hydrographicconditions
Currents
Upwelling
Vertical mixing
19. 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 )
20. Ecosystem function Canopystructure
21. Ecosystem function Canopystructure
22. Ecosystem function Below-ground structure
23. Ecosystem function Epiphyte and epifaunal substratum
24. Ecosystem function Epiphyte and epifaunal substratum
25. Ecosystem function Epiphyte and epifaunal substratum
26. Ecosystem function Wave and current energy damping
27. Ecosystem function Wave and current energy damping
28. Ecosystem function Nutrient, contaminant and sediment filtration and trapping
29. Ecosystem function Nutrient regeneration and recycling
30. Habitat connectivity
31. Habitat connectivity
N
32. Habitat connectivity
33. Habitat disturbances
Natural
Waves
Hurricanes
Animal foraging
Anthropogenic
Eutrophication
Sedimentation
Habitat destruction
Overfishing
34. Natural disturbances Waves
35. Natural disturbances Waves
36. Natural disturbances Hurricanes
37. Blow outs
38. Natural disturbances Animal Foraging
39. Natural disturbances Animal Foraging
40. Natural disturbances Animal Foraging
41. Natural disturbances Animal Foraging
42. Natural disturbances Animal Foraging
43. Anthropogenic disturbances Eutrophication
The process by which a body of water becomes enriched in dissolved nutrients that stimulate the growth of aquatic plant life
44. 45. Eutrophication HABs
[ Harmful Algal Blooms ]
46. Eutrophication HABs
47. Anthropogenic disturbances Sedimentation
48. Anthropogenic disturbances Sedimentation
49. Anthropogenic disturbances Urbanization
50. Anthropogenic disturbances Urbanization
10 km
Shading = >1,000 persons/mi2
From: Planning Commission of Puerto Rico, Office of Land Use
51. Other anthropogenic disturbances -
Propeller scarring
52. Other anthropogenic disturbances - Harvesting
53. Caulerpa
Ballast water
Other anthropogenic disturbances - Invasive species
54. Anthropogenic disturbances Overfishing
55. Anthropogenic disturbances Overfishing
Before Fishing
After Fishing
Jackson et al.,Science293, 629 -637 (2001)
56. Jackson et al.,Science293, 629 -637 (2001)
>3.3107 adult turtles historically1.1106 50-kg turtles today
57. Current research
Orth et al. 2006Bioscience 56(12): 987-996
More seagrass research!!
58. Current research
Effects of water quality on seagrass community productivity and biodiversity in NE Puerto Rico
USGS Water Resources
Data 2004
59. Non-impacted - 7S
Impacted - LC
Study sites Fajardo
60. Biodiversity - Fish
Impacted
Non-Impacted
61. Biodiversity - Fish
*
* From Kopp et al. 2007 Aquatic Botany
62. Conclusions:

  • Nearshore and watershed water quality are poor,

mainly due to sediment not nutrients

  • More stable communities may protect biodiversity (and vice versa)

63. Higher frequency measurements are needed, especially light 64. Long-term studies are needed (study is ongoing) i.e., SeagrassNet.org 65. Seagrass conservation areas and nearshore water quality management are needed in Puerto Rico!