Higher Plants
•
Coastal zone incl intertidal: mangroves/salt marshes; seagrass vegetations: prevention of substrate removal, filtration of water, provision of habitat for animals.

Higher Plants
•
Coastal zone incl intertidal: mangroves/salt marshes; seagrass vegetations: prevention of substrate removal, filtration of water, provision of habitat for animals.
•
Not many 'true marine plants' (seagrasses); others
'surviving in marine environment‘.

Mangroves
•
Tropics! Optimal: evergreen forests; ecological stress
(temperature, salinity): shrubs.

A tide channel with a well-developed mangrove composed of evergreen, salt-tolerant trees.

Dwarf growth of Avicennia in Saudi-Arabia (too cold in winter!)

Mangroves
• Tropics! Optimal: evergreen forests; ecological stress (temperature, salinity): shrubs.
At land-sea interface, salt tolerant forested wetlands.

Typical mangrove growth around an estuary (Tanzania).

Mangroves
• Tropics! Optimal: evergreen forests; ecological stress (temperature, salinity): shrubs.
At land-sea interface, salt tolerant forested wetlands
•
Requirements:
- tropical temps,
- fine-grained alluvium,
- no strong wave or tidal actions,
- salt water (><),
- large tidal range.

Species diversity of mangroves on a world scale.

Rhizophora on (partly sand-covered) coral platform! (Kenya).

Mangroves
• Tropics! Optimal: evergreen forests; ecological stress (temperature, salinity): shrubs.
At land-sea interface, salt tolerant forested wetlands.
• Requirements: tropical temps, fine-grained alluvium, no strong wave or tidal actions, salt water (><), large tidal range.
•
Species-rich: SE-Asia >< species-poor: Africa,
America.

Species diversity of mangroves on a world scale.

Mangroves
• Tropics! Optimal: evergreen forests; ecological stress (temperature, salinity): shrubs.
At land-sea interface, salt tolerant forested wetlands.
• Requirements: tropical temps, fine-grained alluvium, no strong wave or tidal actions, salt water (><), large tidal range.
•
Species-rich: SE-Asia >< species-poor: Africa, America.
•
Adaptations to environment:

Mangroves
Adaptations to environment:
•
Water stress: freshwater plants! energy in inverse osmosis: slow growth, sensitive to extra stress
(pollution).

Mangroves
• Adaptations to environment
•
Water stress
: freshwater plants! energy in inverse osmosis: slow growth, sensitive to extra stress (pollution).
Adaptations:
- fleshy leaves,

Sonneratia alba : detail of a flower (stamens grouped in separate packages); remark the fleshy leaves.

Mangroves
• Adaptations to environment
•
Water stress
: freshwater plants! energy in inverse osmosis: slow growth, sensitive to extra stress (pollution).
Adaptations:
- fleshy leaves,
- thick cuticle + waxy layer,

Mangroves
• Adaptations to environment
•
Water stress
: freshwater plants! energy in inverse osmosis: slow growth, sensitive to extra stress (pollution).
Adaptations:
- fleshy leaves,
- thick cuticle + waxy layer,
- stomata on lower leaf surface & sunken;

thick wax layer cuticle fleshy leaf peltate hairs cuticle thin, “dry” leaf cuticle peltate hairs sunken stomate cuticle thick waxy layer sunken stomate
Left: fleshy leaf with thick cuticle , thick waxy layer , sunken stomata on lower leaf surface.
Right: thin leaf with thick cuticle , peltate hairs and sunken stomata on lower leaf surface.

Mangroves
• Adaptations to environment
•
Water stress
: freshwater plants! energy in inverse osmosis: slow growth, sensitive to extra stress (pollution).
Adaptations:
- fleshy leaves,
- thick cuticle + waxy layer,
- stomata on lower leaf surface & sunken;
- thin leaves: peltate hairs.

Conocarpus (buttonwood) with thin, silvery leaves due to the hairy surface (limitation of evaporation). (Bahamas).

Mangroves
• Adaptations to environment
•
Water stress
: freshwater plants! energy in inverse osmosis: slow growth, sensitive to extra stress (pollution).
Adaptations:
- fleshy leaves,
- thick cuticle + waxy layer,
- stomata on lower leaf surface & sunken;
- thin leaves: peltate hairs.
- + drop roots: absorbing rainwater.

Rhizophora : Well developed drop roots
(direct uptake of rain water) (Papua
New Guinea).

Mangroves
• Adaptations to environment
- Water stress : freshwater plants! energy in inverse osmosis: slow growth, sensitive to extra stress (pollution)
-
Anoxic environment: soil water-saturated -> respiratory roots:

Avicennia -mangrove at high tide (Bahamas): water saturated and thus anoxic soil.

Mangroves
• Adaptations to environment
- Water stress : freshwater plants! energy in inverse osmosis: slow growth, sensitive to extra stress (pollution)
-
Anoxic environment: soil water-saturated -> respiratory roots:
1. Rhizophores + lenticels + aerenchyma.

Rhizophora : extensive development of rhizophores (Papua New Guinea).
Remark also some drop-roots !

Rhizophora : detail of the rhizophores with lenticels and mangrove snails.

Lenticle of an Avicennia -pneumatophore on transverse section: the outer cork tissue
( c ) is torn apart due to increased cell division of cambial and phelloderm cells: gas exchange is hereby made possible but (salt) water cannot intrude (scale bar = 300
µm).

Transverse section through a pneumatophore of Avicennia : the outer periderm (p) = cork cells, cortex (c) = threedimensional network of cells and air spaces, surrounding the central stele (s = vascular system) (scale bar = 300 µm).

Mangroves
• Adaptations to environment
- Water stress : freshwater plants! energy in inverse osmosis: slow growth, sensitive to extra stress (pollution)
-
Anoxic environment: soil water-saturated -> respiratory roots:
1. Rhizophores + lenticels + aerenchyma
2. Pneumatophores on cable roots + +

Avicennia : radiating cable roots under the sand surface, bearing the negative geotropic pneumatophores (pencil roots).

Well developed Avicennia -mangrove at low tide .

Avicennia : at high tide the tips of the pneumatophores (provided with lenticles) remain above water.

Sonneratia alba : the erosion along a mangrove channel made the cable roots apparent.

Mangroves
• Adaptations to environment
- Water stress : freshwater plants! energy in inverse osmosis: slow growth, sensitive to extra stress (pollution)
-
Anoxic environment: soil water-saturated -> respiratory roots:
1. Rhizophores + lenticels + aerenchyma
2. Pneumatophores on cable roots + +
3. Knee roots + +

Bruguiera : rhizophores closely packed to the stem and knee roots .

Bruguiera : knee roots: detail.

Mangroves
• Adaptations to environment
- Water stress : freshwater plants! energy in inverse osmosis: slow growth, sensitive to extra stress (pollution)
-
Anoxic environment: soil water-saturated -> respiratory roots:
1. Rhizophores + lenticels + aerenchyma
2. Pneumatophores on cable roots + +
3. Knee roots + +
4. Buttress roots + +

Xylocarpus granatum : buttress roots (= plank roots).

Xylocarpus granatum : buttress roots.

Xylocarpus granatum : buttress roots.

Mangroves
• Adaptations to environment
- Water stress : freshwater plants! energy in inverse osmosis: slow growth, sensitive to extra stress (pollution)
-
Anoxic environment: soil water-saturated -> respiratory roots:
1. Rhizophores + lenticels + aerenchyma
2. Pneumatophores on cable roots + +
3. Knee roots + +
4. Buttress roots + +
+ epiphytic macroalgae.

Study of the epiphytic algae by Master students (species composition, zonation, biomass).

Sonneratia alba : healthy, raher shaded pneumatophores with thick cushions of mainly red algal epiphytes.

Plunging view on the epiphytic algae: they don’t exclusively cover the pneumatophores, but they also spread on the sandy substrate!

Making a transect along a nylon rope, perpendicular to the tides (relevés every 1 m).

Making notes with a pencil on a plexiglass plate.

Counting, measuring and collecting the pneumatophores.

Mangroves
• Adaptations to environment
- Water stress : freshwater plants! energy in inverse osmosis: slow growth, sensitive to extra stress (pollution)
Anoxic environment : soil water-saturated -> respiratory roots: rhizophores + lenticels + aerenchyma, pneumatophores on cable roots + +, knee roots + +, buttress roots + +, + epiphytic macroalgae.
-
Muddy substrate/tidal effect: vivipary
(propagules)

Bruguiera gymnorhiza : flowers; in the upper flower the corolla and stamens are gone, the calyx and pistil are visible.

Bruguiera gymnorhiza : vivipary: development of the propagules.

Bruguiera gymnorhiza : fully grown propagule: the visible part is mainly the hypocotyl .

Rhizophora : flowers of the new season and propagules of the previous season (the pale part is the stem growing while still attached in the fruit ).

Rhizophora : young plants attached in silt.

Mangroves
• Associated fauna: crabs!! Snails.

Fiddler crabs can locally be extremely numerous.

Mangroves
• Associated fauna: crabs!! Snails.
• Niche diversity!! Canopy; lower part of stems and aerial roots; muddy substrate around roots >< between trees.

Niche diversity in a well developed Sonneratia -vegetation.

Mangroves
• Associated fauna: crabs!! Snails.
• Niche diversity!! Canopy; lower part of stems and aerial roots; muddy substrate around roots >< between trees.
•
Ecological roles of mangroves
• - soil formation by trapping debris (aerial roots!! + filamentous algae);
• - filter land run-off -> removing terrestrial organic matter;

The intricate rootsystems are excellent sediment traps and serve as refugia for organisms against their predators.

Mangroves
• Associated fauna: crabs!! Snails.
• Niche diversity!! Canopy; lower part of stems and aerial roots; muddy substrate around roots >< between trees.
•
Ecological roles of mangroves
- soil formation by trapping debris (aerial roots!! + filamentous algae);
- filter land run-off -> removing terrestrial organic matter;
- habitats for many faunal species (nursery function!)

Mangrove as nursery for numerous marine organisms (such as juvenile fishes).

Fishes of diverse age classes.

A barracuda (predator, carnivore) in the mangrove .

Mangroves
• Associated fauna: crabs!! Snails.
• Niche diversity!! Canopy; lower part of stems and aerial roots; muddy substrate around roots >< between trees.
•
Ecological roles of mangroves
- soil formation by trapping debris (aerial roots!! + filamentous algae);
- filter land run-off -> removing terrestrial organic matter;
- habitats for many faunal species (nursery function!);
- producers of detritus -> offshore productivity.

At outgoing tide dropped leaves are carried away to the lagoon.

But in some seasons large quantities of seagrass leaves and seaweeds ( Sargassum ) are transported into the mangroves and deposited between the root systems.

Detail of the large quantities of seagrass leaves and seaweeds being imported in the mangrove.

Mangroves
• Associated fauna: crabs!! Snails.
• Niche diversity!! Canopy; lower part of stems and aerial roots; muddy substrate around roots >< between trees.
• Ecological roles of mangroves
- soil formation by trapping debris (aerial roots!! + filamentous algae);
- filter land run-off -> removing terrestrial organic matter;
- habitats for many faunal species (nursery function!);
- producers of detritus -> offshore productivity.
•
Mangrove loss: soil reclamation for aquaculture
(shrimps), agriculture, urban development (incl harbours), clear-felling, waste dumping, ...

Heavily cut mangrove. Today the whole mangrove (of which part of it is still visible in the background on this picture) has ‘disappeared’.

Erosion of the beach even resulting in uprooting of the coconut trees.

Mangroves
• Associated fauna: crabs!! Snails.
• Niche diversity!! Canopy; lower part of stems and aerial roots; muddy substrate around roots >< between trees.
• Ecological roles of mangroves
- soil formation by trapping debris (aerial roots!! + filamentous algae);
- filter land run-off -> removing terrestrial organic matter;
- habitats for many faunal species (nursery function!);
- producers of detritus -> offshore productivity.
• Mangrove loss: soil reclamation for aquaculture (shrimps), agriculture, urban development (incl harbours), clear-felling, waste dumping, ...
Upstream pollution (pesticides) and eutrophication!

Mangroves
•
Actual situation of mangrove vegetations worldwide: DESASTROUS!!
1991: the SE Asian coastlines have lost large mangrove areas:
80% in the Philippines, 50% in Thailand and Indonesia, and
32% in Malaysia. Pression going on as greater demands are placed on forest and fishery resources along with land usechanges along coastines and in upland watersheds.
Restoration projects.

Mangroves are crucial for water quality of coastal water and as nursery grounds.

Mangroves are also important for the stability of the coastline.

SALT MARSHES
•
Replacing mangroves in temperate regions.

Optimal development of salt marshes restricted to the zones north and south of the
20°C-belt . (S = summer; W = winter).

SALT MARSHES
• Replacing mangroves in temperate regions.
•
Shrubs, grasses, herbs: HALOTOLERANT.

General view of mud flats (with algae) and salt marshes (with higher plants) at Térénez (Morlaix, Brittany, France).

SALT MARSHES
• Replacing mangroves in temperate regions.
• Shrubs, grasses, herbs: HALOTOLERANT.
•
Important nursery grounds; important for wading birds.

SALT MARSHES
• Replacing mangroves in temperate regions.
• Shrubs, grasses, herbs: HALOTOLERANT.
•
Important nursery grounds; important for wading birds.
•
Requirements for development: similar to mangroves
[ fine-grained alluvium, no strong wave or tidal actions, salt water (><), large tidal range] but at least some freezing temperatures occurring.

SALT MARSHES
• Replacing mangroves in temperate regions.
• Shrubs, grasses, herbs: HALOTOLERANT.
•
Important nursery grounds; important for wading birds.
• Requirements for development: similar to mangroves but at least some freezing temperatures occurring.
• Adaptations to the environment: similar to mangroves:
Water stress: freshwater plants! energy in inverse osmosis: slow growth, adaptation of leaves: fleshy/thin, vegetation sensitive to extra stress (pollution). Anoxic environment: soil watersaturated -> presence of aerenchyma in the plant.

SALT MARSHES
• Replacing mangroves in temperate regions.
• Shrubs, grasses, herbs: HALOTOLERANT.
•
Important nursery grounds; important for wading birds.
• Requirements for development: similar to mangroves but at least some freezing temperatures occurring.
• Adaptations to the environment: similar to mangroves.
• Zonation ≠ succession.

Colonisation of the silty sand by diatoms (unicellular algae).

Fixation of the silt of the mud flats by diatoms (under) and filamentous + tubular green algae (up).

The algae gradually form a continuous felt on the silty substratum.

Germination and growth of the annual glasswort ( Salicornia europaea ) in the felt of algae.

Germination and growth of the annual glasswort ( Salicornia europaea ) in the algal felt.

Spartina townsendii vegetation succeeding the Salicornia vegetation.

Common Saltmarsh-grass ( Puccinellia maritima : red arrows) along the salt marsh cup, followed higher up by Sea-purslane ( Halimione portulacoides : grey coloured: yellow arrows).

Typical view of a salt marsh with a tidal gully (here almost fresh water) with the brown alga Fucus ceranoides (brown arrow) the green alga Ulva intestinalis (green arrows), colonizing Salicornia (blue arrow) and Sea-purslane along the higher banks
(yellow arrow); Térénez.

Dense vegetation of Limonium vulgare at Nieuwpoort.

Zonation of a “ripe” salt marsh with tide channels and marked zonation.

SALT MARSHES
• Replacing mangroves in temperate regions.
• Shrubs, grasses, herbs: HALOTOLERANT.
•
Important nursery grounds; important for wading birds.
• Requirements for development: similar to mangroves but at least some freezing temperatures occurring.
• Adaptations to the environment: similar to mangroves.
• Zonation ≠ succession.
•
Ecological roles: similar to mangroves:
- production (>< uptake) of organic matter;

SALT MARSHES
• Replacing mangroves in temperate regions.
• Shrubs, grasses, herbs: HALOTOLERANT.
•
Important nursery grounds; important for wading birds.
• Requirements for development: similar to mangroves but at least some freezing temperatures occurring.
• Adaptations to the environment: similar to mangroves.
• Zonation ≠ succession.
•
Ecological roles: similar to mangroves:
- production (>< uptake) of organic matter;
- habitat (nursery) for numerous animals;

SALT MARSHES
• Replacing mangroves in temperate regions.
• Shrubs, grasses, herbs: HALOTOLERANT.
•
Important nursery grounds; important for wading birds.
• Requirements for development: similar to mangroves but at least some freezing temperatures occurring.
• Adaptations to the environment: similar to mangroves.
• Zonation ≠ succession.
•
Ecological roles: similar to mangroves:
- production (>< uptake) of organic matter;
- habitat (nursery) for numerous animals;
- stabilization of coastal substratum (root system!!);

SALT MARSHES
• Replacing mangroves in temperate regions.
• Shrubs, grasses, herbs: HALOTOLERANT.
•
Important nursery grounds; important for wading birds.
• Requirements for development: similar to mangroves but at least some freezing temperatures occurring.
• Adaptations to the environment: similar to mangroves.
• Zonation ≠ succession.
•
Ecological roles: similar to mangroves:
- production (>< uptake) of organic matter;
- habitat (nursery) for numerous animals;
- stabilization of coastal substratum (root system!!);
- filtration of coastal run off.

SEAGRASS COMMUNITIES
• MARINE (!) flowering plants; NOT grasses!!

General view on an intertidal segrass vegetation.

SEAGRASS COMMUNITIES
• MARINE (!) flowering plants; NOT grasses!!
• Mainly in tropics, forming extensive meadows, but some species also in colder regions.

SEAGRASS COMMUNITIES
• MARINE (!) flowering plants; NOT grasses!!
• Mainly in tropics, forming extensive meadows, but some species also in colder regions.
•
Requirements for development:
- Salt or brackish water (estuaries); absent in freshwater!!
- submerged (at least part of the day);
- loose substrate;
- best developed on shallow slopes; limited wave action.

SEAGRASS COMMUNITIES
• MARINE (!) flowering plants; NOT grasses!!
• Mainly in tropics, forming extensive meadows, but some species also in colder regions.
• Requirements for development: salt or brackish water (estuaries); absent in freshwater; submerged (at least part of the day); loose substrate; best developed on shallow slopes; limited wave action.
•
Species diversity: 58 spp worldwide; vicariance --> sister species.

SEAGRASS COMMUNITIES
• MARINE (!) flowering plants; NOT grasses!!
• Mainly in tropics, forming extensive meadows, but some species also in colder regions.
• Requirements for development: salt or brackish water (estuaries); absent in freshwater; submerged (at least part of the day); loose substrate; best developed on shallow slopes; limited wave action.
•
Species diversity: 58 spp worldwide; vicariance -> sister species.
•
Adaptations to environment:
- Adapted to saline environment (physiology!);

SEAGRASS COMMUNITIES
• MARINE (!) flowering plants; NOT grasses!!
• Mainly in tropics, forming extensive meadows, but some species also in colder regions.
• Requirements for development: salt or brackish water (estuaries); absent in freshwater; submerged (at least part of the day); loose substrate; best developed on shallow slopes; limited wave action.
•
Species diversity: 58 spp worldwide; vicariance -> sister species.
•
Adaptations to environment:
- Adapted to saline environment (physiology!);
-
Growing under submerged conditions: presence of aerenchyma; vascular bundles limited; thin cuticle, epidermal cells with chloroplasts; stomates absent;

Transverse section through a leaf of wheat: cuticle present, stomata present, no plasts in the epidermis, well developed vascular bundles (vb), no aerenchyma.
Transverse section through a leaf of Halodule wrightii : no cuticle, no stomata, presence of plasts in the epidermis, limited vascular bundles, presence of aerenchyma.

SEAGRASS COMMUNITIES
• MARINE (!) flowering plants; NOT grasses!!
• Mainly in tropics, forming extensive meadows, but some species also in colder regions.
• Requirements for development: salt or brackish water (estuaries); absent in freshwater; submerged (at least part of the day); loose substrate; best developed on shallow slopes; limited wave action.
•
Species diversity: 58 spp worldwide; vicariance -> sister species.
•
Adaptations to environment:
- Adapted to saline environment (physiology!);
- Growing under submerged conditions: presence of aerenchyma; vascular bundles limited; thin cuticle, epidermal cells with chloroplasts; stomates absent;

SEAGRASS COMMUNITIES
MARINE (!) flowering plants; NOT grasses!!
• Mainly in tropics, forming extensive meadows, but some species also in colder regions.
•
Requirements for development: salt or brackish water (estuaries); absent in freshwater; submerged (at least part of the day); loose substrate; best developed on shallow slopes; limited wave action.
•
Species diversity: 58 spp worldwide; vicariance -> sister species.
• Adaptations to environment:
- Adapted to saline environment (physiology!);
Growing under submerged conditions: presence of aerenchyma; vascular bundles limited; thin cuticle, epidermal cells with chloroplasts; stomates absent;
- Withstanding wave action and tidal currents: extensive rhizomes and fleshy roots; supple leaves;

SEAGRASS COMMUNITIES
Succession & zonation
Unicellular algae (diatoms)

Massive development of diatoms on the sand; by their production of slime, sand grains ± stick together.

Massive development of diatoms on the sand; by their production of slime, sand grains ± stick together : detail.

SEAGRASS COMMUNITIES
Succession & zonation
Unicellular algae (diatoms)
-> filamentous algae

SEAGRASS COMMUNITIES
Succession & zonation
Unicellular algae (diatoms)
-> filamentous algae
-> colonizing seagrass species (long internodes)

Pioneer seagrass vegetation in the intertidal = Halodule wrightii and
Halophila ovalis.

SEAGRASS COMMUNITIES
Succession & zonation
Unicellular algae (diatoms)
-> filamentous algae
-> colonizing seagrass species (long internodes)
-> succession

Mid- to lower intertidal pools: Cymodocea rotundata and C. serrulata.

SEAGRASS COMMUNITIES
Succession & zonation
Unicellular algae (diatoms)
-> filamentous algae
-> colonizing seagrass species (long internodes)
-> succession
-> climax vegetation

Intertidal climax seagrass vegetation: Thalassia hemprichii.

SEAGRASS COMMUNITIES
Niches with associated fauna
- on and around the leaves

Detail of Thalassodendron ciliatum.

SEAGRASS COMMUNITIES
Niches with associated fauna
- on and around the leaves
- on and around the stipes

Detail of Thalassodendron ciliatum .

SEAGRASS COMMUNITIES
Niches with associated fauna
- on and around the leaves
- on and around the stipes
- around the rhizomes

SEAGRASS COMMUNITIES
Niches with associated fauna
- on and around the leaves
- on and around the stipes
- around the rhizomes
- banks of dead seagrass leaves washed ashore.

"Banquettes" of leaves of Posidonia oceanica in Sardinia
(Mediterranean Sea).

SEAGRASS COMMUNITIES
Ecological roles
- sediment trapping

Subtidal fringe: detail of Syringodium isoetifolium with cylindrical leaves; remark the sediments being deposited between the leaves!

SEAGRASS COMMUNITIES
Ecological roles
- sediment trapping
- primary producers (incl epiphytic algae!)

Laurencia (red alga) and crustose Corallinaceae epiphytic on a leaf of
Cymodocea.

SEAGRASS COMMUNITIES
Ecological roles
- sediment trapping
- primary producers (incl epiphytic algae!)
- direct food source herbivorous fish, sea-turtles, dugongs

Grazing of epiphytic algae by gastropods.

SEAGRASS COMMUNITIES
Ecological roles
- sediment trapping
- primary producers (incl epiphytic algae!)
- direct food source herbivorous fish, sea-turtles, dugongs
- important habitats for animals (nursery!)

SEAGRASS COMMUNITIES
Ecological roles
- sediment trapping
- primary producers (incl epiphytic algae!)
- direct food source herbivorous fish, sea-turtles, dugongs
- important habitats for animals (nursery!)
- important substrate for attachment (epiphytes!)

Epiphytism : the brown alga Dictyota
(brownish green) and Corallinaceae
(white) epiphytic op Thalassodendron ciliatum in a mangrove tide channel; the brownish colour of the water is the result of seepage from the mangrove.

SEAGRASS COMMUNITIES
Ecological roles
- sediment trapping
- primary producers (incl epiphytic algae!)
- direct food source herbivorous fish, sea-turtles, dugongs
- important habitats for animals (nursery!)
- important substrate for attachment (epiphytes!)
- nutrient stripping.

SEAGRASS COMMUNITIES
Human uses and impacts
- filter system for sewage effluents

SEAGRASS COMMUNITIES
Human uses and impacts
- filter system for sewage effluents
- paper production

SEAGRASS COMMUNITIES
Human uses and impacts
- filter system for sewage effluents
- paper production
- direct food/fodder

SEAGRASS COMMUNITIES
Human uses and impacts
- filter system for sewage effluents
- paper production
- direct food/fodder
- stabilizing sediments

SEAGRASS COMMUNITIES
Human uses and impacts
- filter system for sewage effluents
- paper production
- direct food/fodder
- stabilizing sediments
- diebacks ofter oil spill, thermal pollution, dredging, eutrophication.