- Multiple clades of primary producers: include both algae (attached) and phytoplankton (floating) forms.
- Existence of food in suspension: allows for suspension feeding forms which just capture food "on the fly" (not really possible in most terrestrial environments)
- More diverse, and larger bodied, sediment feeding community
- More diverse overall: majority of clades are marine
Marine realm can be divided into many different divisions:
- Photic Zone vs. Aphotic Zone: Presence or absence of transmitted light, with all that means for photosynthesis
- Intertidal/Littoral: Exposed to air twice daily. Inhabitants must be adapted to change of environment
- Pelagic vs. Benthic: above the sea floor vs. along the sea floor
Marine organisms life habits:
- Planktonic: floating
- Nektonic: swimming
- Benthic: bottom dwelling, including:
- Epifaunal (surface dwellers) vs. infaunal (sediment dwellers)
- Motile (moving) vs. sessile (non-moving)
- "Marine realm" also include fliers, waders, and other terrestrial forms which feed within marine food webs
In Galápagos, we will primarily see Intertidal community, shallow sublittoral community, and shallow pelagic organisms.
Intertidal Community
- Tough to live in full time, as varies between air and water.
- Distinct zonation due to relative amount of exposure, temperatures, etc.
- Lacking big muddy component (either siliciclastic or carbonate) compared to continental coasts or some islands, benthic community is not terribly diverse.
- Also, lacking coral reefs (temperature rather low, and very young islands to begin with), not as many microniches for benthic organisms to inhabit.
- However, nektonic organisms are fairly diverse.
Bases of intertidal community are phytoplankton and algae (a life habit, not a clade!). Most conspicuous is a green alga Ulva lobata (sea lettuce): main food of marine iguanas. Also abundant are various red algae and brown algae.
Benthic suspension feeders:
- Sponges (natural water filters)
- Orange cup corals and hydrozoans
- Pen shells (bivalves)
- Barnacles (crustaceans)
Benthic grazers (a marine "grazer" is an animal that eats sessile organisms, which might be algae or sessile animals):
- Gastropods (snails): some are temporarily exposed to air
- Fireworms (polychete annelids)
- Sea urchins (echinoids), whose broken up skeletons sometimes form a major type of sediment on Galápagos beaches
- Crabs, including:
- Sally Lightfoot crabs (Graspsus graspus)
- Ghost crabs, which make burrows in the sand and mud
- Hermit crabs, which use abandonded gastropod shells for homes
- Fiddler crabs, the males of which have one greatly enlarged claw used as displays
- Marine iguanas (Amblyrhynchus cristatus), the only living marine lizard. It feeds mostly on sea lettuce and brown algae. As cold-blooded animals, they get their heat primarily from the sun, so they can't stay in the cool Galápagos waters for long. On land they spend their time basking on rocks. In order to deal with the salt water they take in, they have evolved very efficient glands to extract the salt and "sneeze" it out as a highly-concentrated brine. Bodies of marine iguanas are crusted with the salt they've sneezed out since their last trip into the water. Like other iguanas, they nest on land.
Sediment feeders, most importantly sea cucumbers (holothuroids), including pepiños (local name for Stichopus fuscus)
Nearshore predators include:
- Sea stars
- Stingrays
- Shore and Wading birds, such as
- Great Blue Heron (Ardea herodias)
- Yellow-crowned Night Heron (Nyctanassa violacea pauper)
- Lava Heron (endemic) (Butorides sundevali)
- Striated Heron (Butorides striatus)
- Flamingos (Phoenicopterus ruber)
- American oystercatchers (Haematopus palliatus galapagensis)
- and more...
Nearshore nektonic organisms, and those that prey on them:
- Humungous diversity of actinopterygians (ray-finned fish)
- Golden rays, Leopard rays, and Manta rays
- Sharks, including white-tipped and black-tipped reef sharks, and hammerheads
- World class diversity of Sea Birds:
- Galápagos penguin (endemic) (Spheniscus mendiculus), wing swimmer
- Tube-nosed birds (Procellariformes), with specialized salt-glands allowing them
to drink sea water & excrete waste through tube in snout. Major procellariforms in
Galápagos include:
- Waved albatross (Phoebastria [formerly Diomeda] irrorata): nearly entire population breeds on Española (some in Isla de la Plata off Ecuador), one of the largest flying birds in the world
- Petrels & Storm-petrels: feed by ãpatteringä (dipping feet on surface to attract fish)
- Pelecaniformes, with totipalmate feet (all four digits on the ground, and all in web)
- Brown pelican (Pelecanus occidentalis urinator): shallow diver, gulping water & fish)
- Boobies (Sulidae): deep divers, catch fish on way back up. In Galápagos,
include:
- Red-footed booby (Sula sula), smallest, make honest-to-goodness nests, live only on edges of archipelago (since they fed far offshore on squid)
- Blue-footed booby (Sula nebouxii excisa), very complex display behaviors, nests near shore and feeds near shore
- Nazca booby (Sula granti), formerly included within Masked booby species, largest of the Galápagos boobies
- Red-billed Tropicbird (Phaethon aethereus), fast flyers, spending most of their time on the wing or in their cliff-side nests
- Frigate birds: steal fish from other birds as well as catching it themselves.
Males have big inflatable throat sacs. Two local species:
- Great Frigatebird (Fregata minor ridgwayi), mostly on Genovesa and San Cristábal, males have slight greenish-sheen on back, more oceanic
- Magnificent Frigatebird (Fregata magnificens magnificens), throughout Archipelago, males have slight purplish-sheen on back, more coastal
- Flightless cormorant (endemic) (Nannopterum harrisi), very fast swimmer, lives only on westernmost islands (near upwelling zone of Cromwell current), foot swimmer
- Gulls, including
- Swallow-tailed gull (essentially endemic) (Larus furcatus), one of the few night-feeding gulls in the world
- Lava gull (endemic) (Larus fuliginosus), very rare
- Brown noddy (Anous stolidus galapengis), infamous as thieves from pelicans
- Green turtles (Chelonia mydas agassizi)
- Marine mammals:
- Galápagos sea lion (Zalophus wollebaeki)
- Galápagos fur sea lion (Arctocephalus galapagoensis)
On the high seas, we will commonly see sea birds that feed far from land. Also, we might notice some big, conspicuous fish, like wahoos.
Also, maybe we'll see cetaceans (16 species of large whale, and 7 dolphins, are known to occur in the Gal‡pagos: some only seasonally).
