Just for you Naomi, Those amazing non-moving algae!
Well to be a complete marine biology page I suppose we
must mention the algae....
It may surprise you to know that the seaweeds we all
know on the sea shore are not actually plants, with a few rare exceptions,
namely the seagrasses.
They are instead classed as algae and are generally
sub-divided into four groups, the chlorophyta (green) the rhodophyta (Red),
the Phaophyta (brown) and the microalgae (small). The first three go to make
up the seaweeds we all know and love, with their lovely decaying smells and
slimy rock properties.
The Ecology of Intertidal Seaweeds.
Algae of Rocky Shores
90% of biomass on rocky shore is brown seaweeds.
Sea weeds can be large - simple designs (Fucus
up to 1m, Ascophylum up to 2-3m)
Seaweeds have to yield to waves - move with them.
Size:
Intertidal algae often smaller than subtidal
relatives:
1. Conditions in intertidal are such that growth is
curtailed, nutrients only available when submerged, stressed due to desiccation
etc.
2. Once seaweeds reach a certain size wave action erodes
material or removes individuals.
They reached workable compromise of size and shape.
Large and tall - large surface area; capture lots of
light but more prone to desiccation.
Degree of Plasticity - seaweeds can adopt different
configurations to meet different environmental conditions. different forms
for different advantages.
Continues throughout life - juveniles not just smaller
version of adults.
Communal living -
+ve - overlapping fronds preserves moisture during
desiccation.
-Ve - at bottom of pile, photosynthetic capacity
decreased.
Zonation:
Dominant spp - Order Fucales
Pelvetia canalicula Top of shore
Fucus spiralis
F vesiculosus
F serratus
Ascophyllum nodosum (sheltered shore)
Himanthalia elongata (exposed shore, Lower
intertidal
Sargassum muticum (EVIL) (Mid- lower tidal
pools).
Zonation on a rocky shore
Microalgae also exist on shore. (Diatoms, Cyanobacteria).
Form microbial film covering rocks.
Provide food source for animals and allow fucoid germule to survive by holding low tide waters.
Algae of Sandy Shores.
Large seaweeds are absent from sandy beaches - mobile sediments.
1. Macrophytes:
Dead or decaying mater from - seaweeds, sea grasses, salt marsh plants at strandlines.
Input can be high - 20-30000 gCm-1yr-1.
Fed upon directly by - talitrid amphipods, isopods, insects.
Dissolved and particulate material leeches into sand, becoming available to infauna.
2. Micro Algae:
Benthic micro algae and phytoplanktonic.
Often dominated by diatoms.
Sheltered shores dominated by benthic microalgae.
Exposed shores dominated by surf zone microalgae.
Intermediate systems have a mix of the two types
a) Benthic Microalgae - bacteria, cyano, autotrophic flagellates, penate diatoms.
Many micro algae live attached to sand grains, dependent on particle and interstitial space sizes - relatively immobile.
Under optimal conditions densities of up to 1000cells cm-3.
In sheltered conditions occur close to surface, exposed is deeper and dispersed.
Changes in oxygenation levels in sand produces zonation pattern of different species distributions.
Some microalgae actively move through sands, vertical migrations associated with tidal cycles and diurnal light patterns, maximizes photosynthesis
b) Surf zone phytoplankton - rich accumulates of diatoms.
Found at water surface associated with bubbles or semi stable foam.
Concentrated by waves and currents, transported horizontally.
Vertical migrations of diatoms - :
diurnal migration from sand - water - foam - sand.
changes in cell construction - rapid cell division in a.m. mucus coats to stick to sand in p.m.
vertical distributions - diurnal.
Horizontal migrations -
On / offshore migration - during day it is onshore, when cells start to sink pushes them beyond surf zone.
Water disturbance of column - moves offshore back to shore - storm disturbances.
Both migrations superimposed onto each other.
A Dinoflagellate, small but interesting, they have this nice tendency to bioluminese and create nasty toxins. All good fun as far as algae go....
3. Primary production - sandy shore algae.
Benthic diatoms - 0-50 gCm-1yr-1
Surf zone - patch formation - 500-2000 gCm-1yr-1, no patches - 20-200 gCm-1yr-1.
Dissolved Organic matter - mucus breakdown, macrophytic material - DOM pool.
Concentrated in surf - yellow foam.
Used by water column microbes, Donnax, sand lickers etc.
DOM conc range from 0.1-5 mgC / Lt.
The thing in the background is actually a sea anemone but I couldn't handle a page with nothing but algae on it, it makes the flesh crawl just thinking about it....
