Seagrass Ecology

Estuarine seagrass ecosystems in North Carolina and Florida

Seagrasses

• Angiosperms (flowering plants) that live life entirely underwater

• Primary productivity is among the highest measured (500 - 4000 g C/m2/year)

• Important feeding and refuge habitat for fishery species (shrimp, scallops, fishes)

• Seagrasses act as sediment stablizers help to filter water

Major polyhaline seagrass species

Scientific name Commonname

Salinity range(ppt)

Zostera marina eelgrass 7 - 35

Halodule wrightii shoal grass 12-35

Thalassia testudinum turtle grass Tolerance: 3.5 - 60Optimum: 24-35

Syringodium filiforme manatee grass 24-35

Halophila spp. “Halophila” 35

Ruppia maritima widgeon grass 2 - 70

Major oligohaline aquatic macrophytes

Scientific name Common Name Salinity range (ppt)

Vallisneria americanum wildcelery or freshwatereelgrass

0 - 9

Potamogeton pectinatus Sago pondweed 0 - 9

Potamogeton perfoliatus redhead grass 0 - 9

Zanichellia palustris horned pondweed 0 -25

Myriophyllum spicatum Eurasian watermilfoil 0 -10

Najas guadalupensis bushy pondweed 1- 15

Seagrass productivity

Species Location Productivity(gC/m

2/day)

Thalassia testudinum FloridaPuerto Rico

0.9 -162.5 - 4.5

Syringodium filiforme FloridaTexas

0.8 - 3.00.6 - 9.0

Halodule wrightii North Carolina 0.5-2.0

Zostera marina North CarolinaRhode Island

0.2-1.70.4-2.9

Habitat Complexity

• Habitat complexity is high in seagrass/SAV

• Predators are inhibited by complexity because the prey have many places to hide

• Densities of many invertebrates (infaunal and epifaunal) and small fishes are greater in SAV than in nearby unvegetated areas

• Seagrass provides a refuge from predation

Types of animals in seagrass

• Infauna: bury in sediment. – Polychaete worms, amphipods, clams, benefit from root and

rhizome mat which protects from predators

– deeper-living animals survive better than shallow-living (Mercenaria > Chione)

• Epifauna: Live on surface of blades and sediment– Meiofauna (harpacticoid copepods), macrofauna (amphipods.

isopods), tube-dwelling sessile polychaetes, gastropods, decapods

– Shoot and leaf complexity provides refuge

• Mobile fauna: Live in water over canopy– fishes swim above canopy, dive into it when predator