Transcript Marine primary producers 10

Coastal Ecology
4. Sand Dunes and Sandy Shores
Druridge Bay, Northumberland
Cape Coast, Ghana
Development of sand dunes
• Sand dunes are an example of succession: if
one progresses inland from the beach one is,
essentially, seeing all the stages through which
a community develops.
• Really, the only way to appreciate the extent to
which the habitat changes on a small scale with
time is to make regular visits at different times of
the year.
• Ultimately dependent upon one grass species:
Ammophila arenaria (Marram grass).
Marram grass
• Tolerates – and, indeed, thrives – on being
buried by sand.
• Sand accumulates in the wind shadow
behind plants.
• Because plants take a long time to decay
the old parts of plants add a fibrous mass
to the sand.
• Xerophytic: fibrous rolled leaves with
stomata on inside.
Marram grass (continued)
Leaf of marram grass
Leaf of marram grass (SEM)
Leymus arenarius: Sea Lyme grass
• Larger, broad blue-green leaves.
Early stages of sand dune system
(mobile dunes)
• Soil essentially just pure sand: well
drained, mobile, lacking in nutrients.
• Very few plant species present: at first,
just Marram Grass and then a few taprooted species start to appear. For
example, Dandelion, Coltsfoot. (Tap roots
supposedly seek for the water table, which
may be many feet below).
Taraxacum officinale: Dandelion
Tussilago farfara: Coltsfoot
Further development of first dunes
• Arrival of leguminous plants such as Bird’s
foot trefoil (Lotus corniculatus) and Rest
harrow (Ononis repens).
• These have root nodules which contain
bacteria responsible for fixing atmospheric
nitrogen (useless) into nitrates (usable by
plants).
• Thus, the ‘soil’ is starting to become
enriched.
Lotus corniculatus: Bird’s foot trefoil
Bird’s foot trefoil (in fruit)
Ononis repens (Rest harrow)
Continuing development
• Further plant growth stabilises the soil.
• Break down of dead plants (and the occasional
buried dead seagull) adds to the nutrients in the
soil and improves its water holding capacity.
• Mosses growing across the surface of the sand
further stabilise the surface.
• Many new plant species appear causing the
vegetation community to become more complex
and diverse.
Sand dune mosses
• Tortula ruralis
Sand dune mosses
• Hypnum cupressiforme
Geranium sanguineum: Bloody
Cranesbill
Calystegia soldanella: Sea
bindweed
Tropical species of bindweed:
Ipomoea pes-caprae
Rosa pimpinellifolia: Burnet Rose
Galium verum: Lady’s bedstraw
Dune slacks
• Behind the dune ridges, and representing a later
stage in development, the dune slacks are
produced when there is a stable cover of
vegetation and the soil has water holding
capacity (partially as a result of humus and
decaying plant remains) and nutrients (from the
decay of generations of plants.
• Number of plant species continues to increase.
Salix repens: Creeping willow
Epipactis palustris: Marsh
Helleborine
Epipactis dunensis: Dune
Helleborine
Corallorhiza trifida: Coralroot Orchid
Dactylorhiza incarnata: Early Marsh
Orchid
Dactylorhiza fuchsii: Common
Spotted Orchid
Dactylorhiza purpurella:
Northern Marsh Orchid
Later stages in development
• The continuing development of the
succession depends on soil types (and
inland land usage to a certain extent –
farmers often encroach onto dunes).
• Acidic soils may develop into dune heath.
• Shrub/tree species cause the development
of dune scrub.
Problems with sand dunes
• Very fragile habitat.
• Fore-dunes susceptible to winter storms.
• Dune system in its entirety is a thin skin of
vegetation – as a result, any damage to the
surface exposes the sand underneath and wind
very rapidly scours this out so that large areas of
uncolonised sand exposed.
• Problems range from rabbits to mountain bikers.
Management techniques
• Variety of strategies are used in the
management of sand dunes:
• Manually replant with marram grass.
• Cover exposed areas with chicken wire.
• Bury old Christmas trees (or, in some
instances, e.g. in Jutland, plant pine
trees).
• Discourage damaging behaviour –
includes fires, camping, bicycles, etc.
Blyth Beach
Common Jellyfish: Aurelia aurita
Common Jellyfish: Aurelia aurita
Common Jellyfish: Aurelia aurita
Compass Jellyfish: Chrysaora hyoscella
Compass Jellyfish: Chrysaora hyoscella
Blue Jellyfish: Cyanea lamarkii
Blue Jellyfish: Cyanea lamarkii
Sea Potato: Echinocardium cordatum
Ensis minor: Razor Shell
Ensis siliqua: Razor Shell
Ensis siliqua: Razor Shell
Scallop
Scallop for the artistically minded
Sea Mouse: Aphrodite aculeata
Sea Mouse: Aphrodite aculeata
Lugworm: Arenicola marina
Lugworm: Arenicola marina
What you cannot see: Diatoms
…and a couple of things to look
out for on tropical beaches