Marine Biodiversity of Southern Sydney Harbour's Journal

Given that we have entered the winter doldrums for photo submissions, a time when cold weather and/or rain make regular visits to the inky depths of southern Sydney Harbour somewhat less appealing, I thought I'd take this opportunity to provide some updates on our environmental DNA (eDNA) sampling and biodiversity detections in Sydney Harbour.

First, we recently published a scientific paper in the journal of Environmental Research that highlights the biodiversity information that can be gained through what we refer to as tree of life (ToL) metabarcoding based on the sampling of seawater, isolation of eDNA in each sample, and running of >10 genetic tests for things like marine mammals, fish, molluscs, echinoderms, sponges, aquatic plants, and bacteria. In this case, in the winter of 2022, we were able to collect water samples at 34 sites around Sydney Harbour, as far west as Paramatta Weir, but also including sites in southern Sydney Harbour like Camp Cove, Parsley Bay, and adjacent Rose Bay (at the infamous dog beach). Here we found that the number of animal and plant species decreased as you moved away from the mouth of Sydney Harbour into the upper reaches of its tributaries. Interestingly, the differences between sites were not driven by one or a few keystone species, but instead it was based on the effects of many individual taxa coming and going into different parts of the harbour. See the Graphical Abstract above for a simple summary. We see this ToL-metabarcoding approach as an important tool to scientists and community groups alike interested in generating baseline biodiversity data in their neck of the woods (or local waters).

We have also now reached the two-year mark of monthly seawater sampling using eDNA mini kits supplied by our collaborators in New Zealand at Wilderlab. We've now had the opportunity to analyze these data, or at the very least 12 months' worth of data from Camp Cove and Parsley Bay. We also cross-referenced these eDNA detections with citizen science observations on iNaturalist as well as in consultation with a local expert that has been recording his observations at these sites on a near weekly basis for the past 20 years!! See the draft map figure above (thanks Dr Yi-Kai Tea for help with the intricacies of formatting in Adobe Illustrator) that shows our regular eDNA sampling sites alongside some of the important iNaturalist observations in Camp Cove and Parsley Bay. Thanks to our citizen science superstar @eschlogl for sharing photos of seahorses, stingaress, prawns, calamari squid, and so much more at these sites.

Finally, see the draft figure above with a word cloud highlighting differences in the ecological attributes of fish (A,B,C) and macroinvertebrate (D,E,F) species detected in Camp Cove and Parsley Bay unique to eDNA detections (A,D), unique to citizen science records (B,E), or shared between the two datasets (C,F). The Venn diagrams above also depict the overlap in the species identified through eDNA (blue) and citizen science observations (orange), where "N" equals the number of species in each data set. In brief, for the fish, we found that 9.4% of the species were unique to eDNA, 66.1% were unique to citizen science observations, and 24.5% were shared between the data sets. Of the species unique to eDNA, 67.5% were based on a single detection in a single month across both sites. For the macroinvertebrates identified to the species-level (think mussels, oysters, crabs, and prawns as examples), we found that 24.1% species were unique to eDNA, 76.3% were unique to citizen science observations, and 2.9% were shared between the datasets. Of the macroinvertebrate species unique to eDNA, 43.9% were based on a single detection in a single month across both sites. In short, biodiversity data sourced from eDNA and citizen science photo submissions appear to go hand in hand, providing a more complete picture of animals in the marine environment when considered in tandem. Team work makes the dream work!

This journal post was written by project leader and iNaturalist member, Dr Joseph DiBattista.

Congratulations to paulmc001, for his amazing Photo Observation of the Month of April of the sometimes elusive, but ultimately precocious Brown Fur Seal (Arctocephalus pusillus) having a "whale" of a time in Parsley Bay.

Brown Fur Seals, more commonly referred to as Australian Fur Seals, have been known to infrequently rest ("nap"), play, as well as haul out and feed along the waterfront of Sydney Harbour, though sometimes to the ire of small boat owners at anchor. Indeed, these are no small animal - females can weigh up to 120 kg and the big bull males can weigh up to 360 kg. Moreover, these animals feed primarily on fish (including those in the Carangidae and Monocanthidae families, as well as buckets of small bait fish), octopus, and squid, leaving a trail of guts, gore, and scales wherever they decide to set up shop and chow down. This species has been recorded as far up the Paramatta River as Birchgrove and Woolwich, noting that sightings west of the Sydney Harbour Bridge are rare on Atlas of Living Australia.

Seal numbers are on the rise, with lots of regular sightings up and down the NSW coast after almost being hunted to extinction for their meat, oil and fur. At the subspecies level (Arctocephalus pusillus doriferus), it remains listed as Vulnerable under the Threatened Species Conservation Act 1995. The closest breeding colony is on Montague Island, off Narooma, where their numbers fluctuate throughout the year based on their northward migrations. Recently, the funded Seabirds to Seascapes project, led by the NSW Department of Climate Change, Energy, the Environment and Water – Biodiversity, Conservation and Science Division, partnering with experts from the Sydney Institute of Marine Science (SIMS), Taronga Conservation Society Australia and NSW National Parks and Wildlife Service, includes a component that aims to monitor the Australian and New Zealand fur seal populations in New South Wales. This habitat-focused initiative is timely, and has my "seal" of approval, pun intended.

This journal post was written by project leader and iNaturalist member, Dr Joseph DiBattista.

I know I sound like a broken record, but congratulations to Erik Schogl, once again, for his amazing Photo Observation of the Month of March of the sea slug Pleurobranchus weberi at Camp Cove in Southern Sydney Harbour. Erik remains atop the leaderboard for the Marine Biodiversity of Southern Sydney Harbour project, with 890 observations and 215 species (including this sea slug). This identification was aided by Hsini Lin, the founder of the Sea Slugs of Taiwan group, and a self taught sea slug expert with a staggering 138315 iNaturalist identifications of species within this amazing group of animals.

This sea slug observation is so important because this species has only recently been recorded in Australia. In fact, there are only 13 total records on Atlas of Living Australia, 12 of those records contributed by iNaturalist citizen scientists and 1 record sourced from the Sea Slug Survey in the Gold Coast, also a citizen science led initiative. As a rundown of the ALA records: one record was contributed by co-Director of the Lizard Island Research Station Dr Anne Hoggett in 2011, two were recorded in 2023 on Queensland's Sunshine Coast, 3 were recorded on Queensland's Gold Coast (one in 2020 and two in 2023), 2 were recorded near the entrance of Lake Macquarie in New South Wales in 2023, and 5 (including our observation of the month) were recorded in Sydney Harbour. The remaining observations in Sydney Harbour were all in Chowder Bay at various points in 2022.

Previously, this species was only known from Indonesia and the Philippines, can get quite large (up to 20 cm), and can be distinguished from closely related species in the size of the mantle tubercles, placement of the white circles relative to their tubercles, and completeness of the circles. I will never say no to a new nudie!

This journal post was written by project leader and iNaturalist member, Dr Joseph DiBattista.

Congratulations to Erik Schogl, once again, for his amazing Photo Observation of the Month of February of the Southern Conger, at least provisionally, in what appears to be a hidey hole in Parsley Bay.

The Southern Conger (Conger verreauxi) is taxonomically stable and has 239 records on Atlas of Living Australia, of which only one record is from Sydney Harbour (in the upper reaches of Middle Harbour). Some of its congeners however, specifically the Eastern Conger (previously known as Conger wilsoni), is much more taxonomically ambiguous. According to John Pogonoski, an Ichthyologist and eel expert at the CSIRO Australian National Fish Collection in Hobart, and following Smith & Stewart (2015), the Australian Faunal Directory recognises Conger monganius (Philipps, 1932) as the valid name for the Eastern Conger. Conger monganius was described from NZ. This months observation is particularly challenging to identify as the placement of the dorsal fin origin in relation to the pectoral fin cannot be seen, which is one of the key characters distinguishing the Southern Conger (C. verreauxi) from its congeners. Indeed, for C. verreauxi, the dorsal fin origin commences at or slightly behind the tip of the pectoral fins. On the other hand, in C. monganius, the dorsal fin origin is well behind the tip of the pectoral fins. Conger verreauxi (153-159) also has more vertebrae than Conger monganius (145-151), noting that colour is a less reliable character to use as it can be variable in all species. There are likely additional Conger species awaiting formal description across Australia's temperate coastline. Thankfully we have a few motivated taxonomists in Australia on the case!

This journal post was written by project leader and iNaturalist member, Dr Joseph DiBattista.

Congratulations to Robbie Belchamber for their photo observation of the month of January of the blue button from the Porpita genus at the northern end of Camp Cove beach in southern Sydney Harbour. This is not a jellyfish, but instead a marine organism consisting of a colony of hydroids or hydrozoan polyps found in most warmer, tropical, and sub-tropical waters of the planet.

The blue button lives on the surface of the sea and moves vertically in the water column by using its float, though mostly moving passively with the ever shifting currents and prevailing winds, with the hydroid colony responsible for capturing planktonic prey via its stinging nematocyst cells. This is one of those "look but don't touch" organisms, as its sting can be an irritant to human skin. Blue buttons are also thought to be moving further and further south down the east Australian coastline with our warming oceans and rapidly changing climate. Please check out this video from the folks at James Cook University to see its beauty in real time.

This journal post was written by project leader and iNaturalist member, Dr Joseph DiBattista.

I am here asking for everyone's help with the habitat restoration component of the Blue World funded Valerie Taylor Prize project on "Marine Biodiversity of Southern Sydney Harbour". Our seahorse hotels have now been deployed for just over 10 months in Parsley Bay but we have not had the opportunity to dive and photograph them for at least 4 months. The four seahorse hotels were installed by Sealife Aquarium on March 23rd, 2023 in approximately 6 metres of water about 10-15 metres north of the swimming net, which is in the process of being replaced with a new one. The approximate location of the four seahorse hotels is flagged in the Google Earth image displayed above. Time permitting, I encourage everyone (anyone!) to get in for a dive in the month of February and report back with photographic evidence demonstrating that these structures remain in place after the new swimming net construction (which began January 22nd, 2024 and included the anchoring of barges to import construction materials), the state of marine growth and accretion on the seahorse hotels themselves, and whether any White's Seahorses are using this habitat as their new home.

This journal post was written by project leader and iNaturalist member, joseph_dibattista Dr Joseph DiBattista.

We thought we'd do something a little different for the Photo Observation(s) of the Month of December, and include four amazing observations of a particular group of fish. And so congratulations to Erik Schlogl and Nic Katherine for their observations of two Common Stingarees (Trygonoptera testacea) (observation one and observation two) and two Coffin Rays (Hypnos monopterygius) (observation one and observation two) at Parsley Bay.

The reason that these observations are both timely and important is that in December 2023, a research project commenced on characterising the Stingaree and Stingray population at Parsley Bay and Camp Cove in Southern Sydney Harbour led by Nic Katherine. Rays in the order Myliobatiformes (which includes cownose rays, devil rays, eagle rays, manta rays, stingarees, and true stingrays, among others) and Torpediniformes (which includes coffin rays, numbfishes, and torpedo rays) started diversifying in the late cretaceous (~100 million years ago), with the former having 63 species and the latter 7 species known from Australia.

In New Zealand for example, these amazing creatures are believed to be spiritual guardians (or Kaitiaki) protecting the shellfish beds within their harbours and estuaries. In Māori culture, a Stingray barb, deeply thrust in, which cannot be withdrawn, is a metaphor to describe an idea that has taken hold in the mind or a grudge between people that was difficult to overcome. Nicole is excited to learn more about the amazing lives of rays right here in Southern Sydney Harbour.

Nicole's first observation at Parsley Bay as part of her standardised, "timed swim" visual survey approach was a 2 metre Smooth Stingray (Bathytoshia brevicaudata), gliding around and underneath the wharf, eating the bait from the sea floor discarded by fishers on the jetty. The Smooth Stingray is the largest species in the world within the Dasyatidae family of true stingrays. On her first survey at Parsley Bay, Nicole observed one Smooth Stingray, ten Estuary Stingrays (Hemitrygon fluviorum), two Kapala Stingarees (Urolophus kapalensis), one Coffin Ray (Hypnos monopterygius), and three Common Stingarees (Trygonoptera testacea). Not bad for her first time out to survey rays in Parsley Bay!

This self-directed project is supported by Dr Joseph DiBattista, now at Griffith University in the Gold Coast, and complementary data collected by fellow citizen scientists as part of this Marine Biodiversity in Southern Sydney Harbour iNaturalist page. The project aim is to learn more about the diversity and residency of rays in Southern Sydney Harbour. Nicole has been enjoying the experience of immersing herself in the rays world, with some of the juveniles dancing and chasing one another in the shallow waters, whereas others were more cryptic, tucked beneath overhangs or covering themselves with sand. The surveys will continue over the next 4 months.

This journal post was written by project leader and iNaturalist member, Dr Joseph DiBattista, as well as iNaturalist member, Nic Katherine.

Congratulations to Karolyn Landat for their Photo Observation(s) of the Month of November of the sea slug from the Elysia genus at Camp Cove in southern Sydney Harbour, also observed on the same day here. This genus of colourful sea slugs is nested within the Plakobranchidae family, but do not be fooled! Even though they superficially resemble nudibranchs, they are not closely related to them at all. Instead they are sacoglossans, sometimes referred to as the solar-powered sea slugs.

At least some species of Elysia sea slugs have extraordinary feeding strategies. When nibbling on their primary food source of algae, they often retain the associated chloroplasts in the lining of their digestive tract, enabling them to survive solely by photosynthesis (without further feeding) for several months at a time. Other species of this genus can be stressed to sadistic extremes. Indeed, some Elysia are capable of regenerating their entire body anew from a severed head (gasp!!!). The observation by Karolyn Landat may be the elusive Elysia australis, but this will require a few more experts providing identification suggestions on iNaturalist given that there are over 100 species in the genus, many with ambiguous taxonomy.

This journal post was written by project leader and iNaturalist member, Dr Joseph DiBattista.

Congratulations to the "Goby Whisperer" Erik Schlogl for his Photo Observation(s) of the Month of October of the Broad-banded Shrimpgoby (Amblyeleotris periophthalmus) from Parsley Bay in southern Sydney Harbour, and the Redspotted Shrimpgoby (Amblyeleotris ogasawarensis) from Camp Cove. The former Broad-banded Shrimpgoby represents the very first record from Sydney Harbour, and a southern range extension from South West Solitary Island in NSW. This is also only the 34th record of this species for all of Australia. Given the time of the year (spring) and size of this photographed fish, this tropical species may have even survived the unseasonably warm 2023 Sydney winter. For the latter Redspotted Shrimpgoby, this represents only the second observation from Sydney Harbour, ever, and only the 16th record for all of Australia. The other Sydney Harbour observation was also in Camp Cove, and no surprise, also by Erik Schlogl.

Shrimpgobies are curious beasts in that they form mutualistic relationships with alpheid shrimps, even sharing the same burrows. The shrimp has poor eyesight and so it perpetually builds the burrow while the able-eyed goby serves as a sentry at the burrow entrance. Each time the shrimp emerges from the burrow entrance, it rests one of its antennae on the body of the goby. If the goby detects danger its body quivers to alert the shrimp. If the threat escalates, the goby darts straight back into the burrow. The shrimpgobies on the other hand, feed by filtering mouthfuls of sand through their gill rakers at points near their burrows in search of benthic invertebrates.

This journal post was written by project leader and iNaturalist member, Dr Joseph DiBattista.

I'd like to congratulate user eschlogl for his Photo Observation of the Month of September of a Red-lined Bubble Snail (Bullina lineata) from Camp Cove. Erik has been on an absolute tear in the month of September, submitting 53 observations from Parsley Bay or Camp Cove alone, which represents 90% of the total input to the Marine Biodiversity in Southern Sydney Harbour project in that month. All of these observations are now "Research Grade", bar this goatfish, this sea urchin, this sponge, this wrasse, this leatherjacket, and this cardinalfish.

The Red-lined Bubble Snail is found throughout the tropical and subtropical Indo-West Pacific intertidal zone, but generally subtidally in temperate locations like Sydney Harbour, where it can be found in moderate numbers, then not again for years. Mini boom and bust perhaps? It is an interesting species in that it displays an intermediate phenotype and phylogenetic placement relative to its heavily shelled and lightly shelled congeners. You also cannot help but notice the spirally grooved shell with a characteristic pattern of pink lines. This species is thought to feed primarily on polychaete worms. Yum, yum, yum...

The observation of this species is a reminder for the Annual Sea Slug Census that runs at a range of Australian locations from the Gold Coast to Melbourne and offshore on Lord Howe Island. This census is now well and truly entrenched in Australian citizen science circles, and regularly makes the news. The initiative represents a rapidly expanding citizen science program in which volunteers photographically record observations of sea slugs during nominated events. The observations contributed by citizens have led to much improved distributional data for sea slugs, the discovery of new species, increasing evidence of poleward range extensions, all of which can act as key indicators of our changing environment. Indeed, sea slugs serve as "canaries in the coal mine" based on their short generation times, which means that they rapidly adapt to changing environmental conditions (i.e., shifting temperatures and food availability). Southern Cross University (SCU) marine scientist Professor Steve Smith helped establish the first census in 2013 at Nelson Bay in New South Wales. Keep an eye out for calls to action later in the year in your local area.

This journal post was written by project leader and iNaturalist member, Dr Joseph DiBattista.