Pattern and Process in a Threatened Seagrass Community

Pattern and Process in a threatened seagrass community

Dynamics and habitat use by sessile epifaunal invertebrates in Posidonia australis By Marie-Claire A. Demers

Supervisors: Andy Davis & Nathan Knott Seagrass Ecosystems

• Seagrass meadows have a high ecological value

• Global seagrass decline Disturbed seagrass meadow

• Posidonia australis is vulnerable to disturbance.

Posidonia australis Seagrass associated organisms

Seagrass associated community (Seagrasswatch) Epifaunal invertebrate community

The assemblage of sessile epifaunal invertebrates associated with seagrass ecosystems is essentially unknown.

Sponge (Tedania sp.) Ascidian (Botrylloides leachi) Epifaunal invertebrate community

• Australian Faunal Directory • World Porifera Database • Online Zoological Collections of Australian Museums • Museum Victoria • Queensland Museum Epifaunal invertebrate community

• Australian Faunal Directory • World Porifera Database • Online Zoological Collections of Australian Museums • Museum Victoria • Queensland Museum • Port Phillip Bay Taxonomy Toolkit Epifaunal invertebrate community Epifaunal invertebrate community Epifaunal invertebrate community Sessile epifaunal invertebrates

Fig. 1: Percentages of habitats where sponges were collected . This review of 111 papers was sourced from ‘web of knowledge’. Papers that studied more than 1 habitat were divided into percentages of each habitat sampled for a total of 100%. Sessile epifaunal invertebrates

Reefs, rock, boulder and pebble Mud Seagrass seagrass distribution Sand Mangrove Algae

Reefs, rock, boulder and pebble Mud Seagrass seagrass distribution seagrass distribution Posidonia distribution Sand Mangrove Algae

Reefs, rock, boulder and pebble Mud Seagrass seagrassSeagrass distribution seagrass distribution Posidoniaseagrass distribution distribution Posidonia distribution SandPosidonia australis distribution Sand Mangrove Mangrove Algae

1. Investigate spatial patterns of distribution. 2. Determine biotic and abiotic drivers of distribution.

Botrylloides leachi Callyspongia sp Haliclona sp. Study Area Sponge identification

1. Species Description 2. Collect specimen Sponge morphs (Phoriospongia sp.) Sponge specimen 3. Extract spicules - Acid - Bleach

Spicule extraction Spicules Sponge identification

Sponge Identification Guide • High abundance and diversity • Catalogued 24 sponge species and 9 ascidian species • Confirmation by expert

Sponge Identification guide Kindom Phylum Class Order Family Genus Species

Kindom Phylum Class Order Family Genus Species

Chondrosida Halisarcidae Halisarca Halisarca laxus

Dictyoceratida Thorectidae ? ?

Haliclona sp.

Chalinidae Haliclona

Gelliussp.

Haplosclerida Porifera Demospongiae Callyspongia sp.1

Callyspongidae Callyspongia Callyspongia sp.2

Callyspongia sp.3

Chondrosida Halisarcidae Halisarca Halisarca laxus Chondropsidae Phoriospongia Phoriospongia sp.

Dictyoceratida Thorectidae ? ? Poecilosclerida Coelosphaeridae Lissodendoryx Lissodendoryx sp. Animalia Haliclona sp. Tedaniidae Tedania Tedania sp. Chalinidae Haliclona

Gelliussp. Botryllidae Botrylloides Botrylloides leachi

Haplosclerida Porifera Demospongiae Callyspongia sp.1 Pleurogona Herdmania Herdmania grandis

CallyspongidaePyuridae Callyspongia Callyspongia sp.2 Pyura spinifera

Pyura Chordata Ascidiacea Callyspongia sp.3 Pyura stolonifera

Chondropsidae Phoriospongia Phoriospongia sp. Cnemidocarpa Cnemidocarpa pedata Stolidobranchia Styelidae Poecilosclerida Coelosphaeridae Lissodendoryx Lissodendoryx sp. Animalia Styela Styela plicata

Tedaniidae Tedania Tedania sp.

Botryllidae Botrylloides Botrylloides leachi

Pleurogona Herdmania Herdmania grandis

Pyuridae Pyura spinifera

Pyura Chordata Ascidiacea Pyura stolonifera

Cnemidocarpa Cnemidocarpa pedata Stolidobranchia Styelidae

Styela Styela plicata Experimental design

Spatial distribution • 6 locations • 2 sites • 6 transects of 1 x 25m Experimental design

• Abundance • Diversity • Size (cm3) • Choice of substrata

Tethyidae family Experimental design

• Abundance • Diversity • Size (cm3) • Choice of substrata

Tethyidae family Experimental design

• Abundance • Diversity • Size (cm3) • Choice of substrata Experimental design

• Abundance • Diversity • Size (cm3) ? • Choice of substrata ?

? Experimental design

• Abundance • Diversity • Size (cm3) • Choice of substrata Experimental design

• Sponge individual • Recruits < 1cm3 • Not always visible • Morphospecies • Size (probably overestimated) Sponge sampling

Haliclona sp. Additional data

Abiotic Factors • Meadow attributes • Water quality measures Biotic Factors

2 • Seagrass condition Seagrass condition measurements within 0.25m quadrats • Abundance of spongivorous fish

Chinaman Leatherjacket (Nelusetta ayraud) Spatial distribution

SPONGE ASCIDIANAbundance 45

40 x =15

30 x = 2 25

Abundance individuals of Abundance Significant 10

5 difference across

0 sites BB_1 BB_2 CB_1 CB_2 HB_1 HB_2 BW_1 BW_2 PP_1 PP_2 LB_1 LB_2 Location_Site Spatial distribution

SPONGE ASCIDIANDiversity 8

7 x = 4

6 5 x = 1

4 Diversity 3

2 Significant

1 difference across

0 BB_1 BB_2 CB_1 CB_2 HB_1 HB_2 BW_1 BW_2 PP_1 PP_2 LB_1 LB_2 sites Location_Site Spatial distribution

3000 Volume 2500 x = 775 3

2000 cm

) 3

1500 Volume (cm Volume

1000 Significant 500 difference across

0 sites BB_1 BB_2 CB_1 CB_2 HB_1 HB_2 BW_1 BW_2 PP_1 PP_2 LB_1 LB_2 Location_Site Spatial Distribution

Choice of substrata: - mussel clumps - Polychaete tube - rock & reef - shells Mussel from mussel clump - seagrass sheath (Trichomya hirsuta), - peduncles (flowering spike) - sponges and ascidians Polycheate tree (Eunice impex) Spatial Distribution

1.8

1.6

1.4

1.2

1.0

0.8 Abundance Abundance SS 0.6

0.4

0.2

0.0 0 1 2 3 4 5 6 7 ‘SS’ individual growing on a Tedania sp. individual p=0.01 Sponge Diversity y = 0.2344x - 0.1172 R² = 0.4835 SS settle on other sponges Spatial Distribution

2 Haliclona

2 Abundance Abundance 1

Chalinidae Haliclona sp. 0 0 1 2 3 4 5 6 p=0.006 Depth (m) y = -0.9566x + 4.3739 R² = 0.5509 Relationship with photosymbionts? Spatial Distribution

2 Haliclona

2 Abundance Abundance 1

0 Shoot count in Posidonia australis 0 20 40 60 80 100 120

P. australis Shoot Count y = 0.0515xp=0.03 - 2.1256 R² = 0.3756 Dense meadow provides more substrata? Conclusion

Abundance, diversity, size and substrata were highly variable among sites

Chondropsidae, Phoriospongia sp . ‘Red with prominent veins’ ‘Navy blue encrusting’ ‘Brain-like orange sponge’ Thank You

Manipulative experiment – Fish exclusion cages