Ocean plants

Maia McGuireFlorida Sea Grant Extension Agent

Terminology

• Aquatic• Estuarine• Freshwater• Marine• Emergent• Floating• Submerged

• Phytoplankton• Algae• Seagrass• SAV (submerged

aquatic vegetation)• True plant

Phytoplankton

• Mostly single-celled, photosynthetic, microscopic plants

• DIATOMS are the most abundant type of phytoplankton—they have a silica “housing”

• DINOFLAGELLATES often produce toxins (and red tides!); some bioluminesce

Activity

• Design and construct a plankter

Algae blooms• Usually a response to increased nutrient levels• Phytoplankton reproduce by dividing, creating

high concentrations (“blooms”)• Nutrient loading can be natural (upwelling) or

related to runoff from land

Red tide

• Bloom of a type of dinoflagellate• Algae release a chemical that goes into the

water and also into the air– Causes respiratory difficulties to humans– Toxic to fish and sometimes to marine mammals

Red tide (cont.)

• Blooms form offshore in Gulf of Mexico

• Can bloom in any month of the year

• Blooms can last for weeks to months; may be lengthened by runoff from land (?)

Multi-cellular plants…

• Algae– Not considered true plants—no roots, flowers,

vascular system– Often called “seaweed”– Often use holdfasts to attach to the substrate– Different groups of algae contain different types of

chlorophyll– Green algae, brown algae, red algae

Reproduction in algae

• Sexual reproduction involves production of spores, which produce a gametophyte, which produces gametes

Green algae

• Contain chlorophyll a and b• Examples: sea lettuce (Ulva lactuca), dead

man’s fingers (Codium fragile)

Some make calcium carbonate skeletons

Brown algae

• Contain chlorophyll a and c• Includes Sargassum seaweed

Red algae

• Contain chlorophyll a• Source of agar, carrageenan (used in many

food products• Few have common names• Often finely branching

Calcareous red algae

• Often found on coral reefs—help “cement” the reef surface

Activity

• Pressing seaweed

Seagrasses

• Fully submerged marine plants; true angiosperms– True roots, vascular system, flowers– Reproduce asexually using rhizomes

• 6-7 species; 3 common– Turtle grass, Shoal grass, Manatee grass– Star grass, Paddle grass, Johnson’s seagrass, – Widgeon grass (freshwater grass with high

salinity tolerance)

http://fmel.ifas.ufl.edu/habitat/seagrass_parts.shtml

Thalassia testudinumTurtle grass

• Largest and most robust of Florida’s seagrasses

• Flat, wide (4-12 mm) leaf blades (10-35 cm in length)

• 2-5 leaves per shoot• Forms extensive meadows

Halodule wrightiiShoal grass

• Early colonizer of disturbed areas or areas too deep or shallow for other seagrasses– Tolerates wide range of T, S

• Leaves flat (1-3 mm wide), 10-20 cm long

• Tips of leaves have 2-3 points

Syringodium filiformeManatee grass

• Leaves are round (like spaghetti); 1-1.5 mm in diameter; length varies but can reach 50 cm

• Commonly found mixed with other seagrasses or in small monospecific patches

Halophila engelmanni, H. decipiens, H. johnsonii

• Relatively sparsely distributed • Paddle-shaped leaf blades• Johnson’s seagrass is listed as a threatened

species

Ruppia maritimaWidgeon grass

• Often found alongside Halodule in areas of lower salinity

• Important food for waterfowl

• Primarily a freshwater plant

Seagrass distribution

Thalassia testudinum

Syringodium filiforme

Halodule wrightii

Halophila engelmanii

Halophila decipiens

Halophila johnsonii

Ruppia maritima distribution

Seagrass biology• Growth– Thalassia blades can grow as much as 1 cm/day– Growth is slowed by cooler temperatures– Extremes in temperatures (hot or cold) can kill

leaf blades– Optimal temperature range 20-30° C– Optimal salinity range 24-35 ppt– Extensive seagrass beds not found deeper than

10-15 m (light and pressure are both factors)

Zonation

• Halodule grows in shallowest water and has highest tolerance to exposure

• Thalassia is most dominant; forms large meadows in waters up to 10-12 m deep

• Syringodium forms meadows in deep water (up to 15 m)

• Halodule and Halophila can grow in even deeper water, but sparsely

Productivity

• Highly productive ecosystems• Important food source, for grazers and as

detritus

Seagrasses provide habitat

• Many species of fish• Molluscs (e.g. scallops, snails)• Shrimp, crabs and other crustaceans• Worms

Threats to seagrasses

• Physical damage– Dredging, prop scars/blowouts

• Eutrophication• Salinity stress• Temperature stress

Mangroves

• Emergent plants• Very salt-tolerant• Have adaptations to deal with salt and wave

action• Occur in zones• Three species in Florida

Red mangrove

• Rhizophora mangle• Has prop roots to

stabilize tree

Black mangrove• Avicennia germinans• Has “pneumatophores”

(breathing roots)• Salty leaves

White mangrove

• Laguncularia racemosa

Ocean stewardship

• Read “A new home for an old friend” to teach kids that aquarium plants should not be dumped into ponds or the ocean

• http://www.usc.edu/org/seagrant/caulerpa/index.html