Marine
Care Ricketts Point Inc.
2005/6 Survey
of Intertidal Marine Life
Aim.
To record
all visible species of marine plants and animals and detect trends over time.
Sites and Surveys.
Five shore platforms, including
one outside the sanctuary, were surveyed four times a year (summer, autumn,
winter and spring), 20 surveys per year in all.
RESULTS
1a. Total number of sanctuary species recorded: 62.
Comment. This compares with 51 species the year before.
1b. Number of species found at each survey site (first
figure is 2004/5, second figure is 2005/6):
Table Rock Platform, 35, 49
Tea House Reef, 36, 48
Banksia Point Platform, 41, 45
McGregor Rock Islet, 42, 48
Sanctuary (above four sites),
51, 62
Picnic Point (control site),
35, 40
Comment. Biodiversity (number of species)
appears to have improved by 22% (from 51 to 62 species) on sanctuary platforms
over the year and 14% (from 35 to 40 species) at the control site (Picnic
Point).
The table also shows that numbers improved for all
sites but particularly at Table Rock Point which has taken a narrow lead in
biodiversity.
2. Approximate percentage of species, by tidal
position (figures are for low tide, mid tide, high tide):
60%, 35%, 5%
Comment. Clearly more species are found closer
to the water (low tide). A probable reason is that it is tougher to survive at
high tide because of the longer periods (up to 6 hours or more) out of the
water. Water, of course, is the exchange medium for nutrients, plankton,
oxygen, CO2 and other gases etc. It also protects against temperature extremes.
High tide dwellers can tolerate high tidal conditions partly because they have
special adaptions. They also have fewer competitors
for food and space than species at mid and low tide.
We should note from the above figures that trampling
damage to biodiversity (no. of species) may be much greater per person
trampling at low tide levels than at high tide levels. However, to estimate the
biomass damage we would also have to consider density (or numbers) of organisms
at the various tide levels. A rough indicator of this density factor is gained
from the fact that 95% of the most common 20 organisms were found at low or
medium tide zones.
3. Number of species found, by season (measured
through 2005 / 2006):
(figures are for Autumn 05,
Winter 05, Spring 05, Summer 06)
Table Rock, 30, 29, 35, 38
Tea House Reef, 27, 33, 34,
35
Banksia Reef, 22, 34, 29, 32
McGregor Islet, 31, 40, 28,
32
Picnic Point, 25, 24, 32, 36
Totals, 135, 160, 158, 173
Comment. The patterns to emerge from the table
are that numbers increased at all sites from spring to summer and increased at
all sites from Autumn 2005 to Summer 2006.
PHYLUM ANALYSIS
Definition of Phylum: This is a division of living things that arose from a
separate branch of evolutionary development. Thus all the three seaweeds are
separate phyla and followed different evolutionary paths.
4a. Number of Phyla represented (all platforms): 10
Comment. This is a surprising number of phyla to
be found in such a tiny area as a shore platform. The average person would
generally be aware of only a few phyla on land: chordates, insects, worms,
flowering plants and conifers. Thus, the phyla-diversity on shore platforms
appears to be relatively large.
4b. Phyla, and number of species in each, 2005/6
(first figure is Sanctuary Reefs, second figure is Control Site (Picnic Point):
Green Seaweeds, 7, 3
Brown Seaweeds, 9, 2
Red Seaweeds, 2, 2
Cnidaria (Anemones,
jellies etc), 3, 3
Echinoderms (Stars,
urchins, etc), 3, 5
Molluscs
(Shellfish etc), 25, 18
Crustaceans
(Crabs, shrimps, etc), 8, 4
Annelida (Segmented
worms), 2, 1
Chordata (Sea
squirts, etc), 2, 2
Bryozoans, 1, 0
Comment. Molluscs,
notably shellfish, dominate. They are well adapted to survive for short periods
out of the water and have hard shells to ward off predators that have such easy
access to prey. However, some phyla may be underrepresented because of human
interference. Crabs, for instance, have been a target of both
children and poachers, as well as their natural predators - birds, fish,
molluscs and so forth.
5. Record number of species found in a single survey
(figures are for 2003/4, 2004/5, 2005/6):
Table Rock Point, 25, 29, 35
Tea House Reef, 26, 26, 34
Banksia Point, 26, 30, 32
McGregor Rock, 33, 35, 38
Picnic Point, 26, 28, 32
Comment: These figures suggest what is
indicated generally by the surveys: that biodiversity is increasing from year
to year. However some species of sea stars and crabs may have diminished since
the sanctuary was declared. Also, improvement in the over-all number of species
may be partly the result of better observational techniques and awareness.
List of all
inter-tidal platform species identified during 20 surveys, Autumn
05 to Summer 06.
Inter tidal Survey Sheet
KEY: C: Coastal Invertebrates of
Green Seaweeds, 7 species
Caulerpa geminate, S97
Caulerpa remotifolia, S99
Caulerpa vesiculifera, S100
Codium fragile, S97
Enteromorpha compressa, E29
Enteromorpha intestinalis, S89
Ulva sp, S88
Capreolia implexa (goldy brown tufts or mat)
Caulocystis uvifera, S81
Colpomenia sinuosa, S64
Cystophora moniliformis, S79
Ecklonia ariega, S74
Ectocarpus fasciculatus, S61
Hormosira banksii, S13
Cnidaria, 3 species
Actina tenebrosa, E126
Anthothoe albocincta, E127
Aulactinia veratra, E127
Coscinasterias calamaria (muricata), E348
Pateriella calcar, E345
Tosia australis, E337
Molluscs, 25 species
Notoplax subspeciosa
Plaxiphora albida, E224
Ischnochiton ariegates, C14-16, E 220-1
Bembicium melanostomum, E245
Bembicium nanum, E244
Cominella lineolata, E262
Lepsiella vinosa, E258
Nodilittorina unifasciata, E245
Thais orbita,
W18
Austrocochlea odontis, E241
Austrocochlea porcata, E240
Austrocochlea concamerata, E241, photo
E244
Battillaria verata, (australis), E247
Nerita atramentosa, E244
Turbo undulates, E242, W18
Cellana tramoserica, E233
Collisella granulose, W21
Notoacmea flammea?,
E236, C32
Patelloida alticostata, E234
Onchidella patelloides, E269
Siphonaria diemenensis, E267
Bivalves
Electroma Georgiana, E290
Mytilus planulatus (edulis), E286
Saccostrea glomerata (oyster), E295
Crustaceans. (Phylum Arthropoda), 8 species
Shrimp
Palaemon serenus, E191
Barnacle
Balanus variegates, C108
Elminius modestus, E175, W25
Crabs
Brachynotus spinosis, E215
Carcinus maenas, E208, W24
Helograpsus haswellianus, E214
Nectocarcinus integrifrons, E209
Worms (Phylum Annelida), 2
species
Perinereis sp. (worm), E158
Galeolaria caespitosa (d =dead), E162
Phylum Cordata, 2 species
Alabes dorsalis (Eel), E413
Oyster Blenny, 529
Muraenochthys breviceps, E404
Bryozoans, 1 species, E321-326 (ID ?)
Additional species found at the control site only:
Allostichaster polyplax, E350
Heliocidaris erythrogramma, E365
Pyura stolonifera (Conjevoi), E379, W27
Birds (all sites): Silver Gulls, Pacific Gulls, Crested Terns, Pelicans,
Pied, Little Pied and Little Black Cormorants.