Sponge and sea squirt garden
Sponges and sea squirts are filter-feeders that attach and grow on rocky reefs. While sponges are invertebrates, sea squirts are thought to be an evolutionary link between invertebrates and vertebrates as, for the larval part of their life cycle, they have a primitive backbone. Sea squirts come in a wide variety of colours and shapes and can be solitary or grow in connected colonies.
Sponges are most common on boulders on the northern side of Cook Island Aquatic Reserve but can be found in most habitats around the island.
Sea squirts are found in the same areas of the aquatic reserve as sponges, though they are less abundant than sponges in the northern section. In the western and southwestern parts of the aquatic reserve, sponges and sea squirts are less obvious, nestled among corals, algae, anemones and feather stars.
Marine life
Sponges and sea squirts benefit all organisms within the aquatic reserve. They filter or clean the water, much like an aquarium filter, extracting food particles and debris while pumping seawater through their bodies. They also provide habitat for many invertebrates, like small shrimp, crabs, snails, and brittle stars, that can live on or in their bodies.
Small fish can be found amongst the sponge and sea squirt garden such as the bicolour combtooth blenny.
Despite containing chemical compounds that deter most predators, sponges are an important food source for nudibranchs and hawksbill turtles. Some species of nudibranchs, sea stars, worms and molluscs feed on sea squirts.
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Sponges are most common on boulders on the northern side of Cook Island but can be found in most habitats around the island.
Sea squirts are found in the same areas as sponges, though they are less abundant in the northern section. In the western and southwestern parts of the aquatic reserve, sponges and sea squirts are less obvious, nestled among corals, algae, anemones and feather stars.
Mountainous pillow sponge living among turfing algae on bedrock (Photo: Ecological Service Professionals)
A branching sponge rising above a bed of turfing algae (Photo: Brigitte Sommer)
Orange-spouted sea squirt (Photo: Ecological Service Professionals)
Sandy boots sponge (left), ringed fleshy coral (middle), and a colony of red-flask sea squirts (right) (Photo: Ecological Service Professionals)
Blue sea star(Linckia laevigata) moving over a seasquirt garden covered in turf algae (Photo: Gary Shuttleworth)
Bicolour combtooth blenny (Ecsenius bicolor) Sponge and seasquirt gardens (among articulate coralline and turf algae) (Photo: Rudi Vir)
Solitary (Herdmania) sea squirt covered in turfing algae (Photo: Ecological Service Professionals)
