Syd­ney sub­merged

There’s a wild world thriv­ing in the me­an­der­ing wa­ter­ways and coastal strip of our largest city.

Australian Geographic - - Contents - STORY AND PHO­TOG­RA­PHY BY JUSTIN GIL­LI­GAN

Be­neath the fa­mil­iar wa­ters of our largest city, a wild world is thriv­ing.

IHAVE A SUN­RISE DATE WITH A SEA­HORSE. It’s at Manly Cove, so I’m up early, driv­ing across Syd­ney Har­bour Bridge, rac­ing the ris­ing sun. The traffic is al­ready a headache; Google Maps shows a fur­ther de­lay in my pre­dicted ar­rival time; and I still need to f ind a car park, get my dive gear to­gether, check my cam­era and lo­cate my muse – po­ten­tially tricky con­sid­er­ing its tiny size and cryp­tic ap­pear­ance and be­hav­iour. As an un­der­wa­ter pho­tog­ra­pher, I work mostly away from ma­jor ur­ban cen­tres. But here I am, turn­ing onto the no­to­ri­ously hec­tic Mil­i­tary Road and driv­ing with barely enough el­bow room to­wards Syd­ney’s pop­u­lous North­ern Beaches. I ar­rive as the pas­tel pink and blue hues of f irst light colour the sky and quickly en­ter the wa­ter. Fin­ning along the sandy bot­tom to­wards the net of Manly Cove’s swim­ming en­clo­sure, the wa­ter is sur­pris­ingly clear as blue swim­mer crabs and har­vest cut­tlef ish hus­tle for my at­ten­tion.

Min­utes later I f ind my quarry – a charis­matic crea­ture, just 15cm long, cov­ered in hard body ar­mour and grasp­ing the net with its pre­hen­sile tail. The stress of the morn­ing rush hour melts away with the ris­ing sun as I cap­ture a por­trait within the last shafts of dawn light.

Syd­ney’s sun-span­gled wa­ters are cen­tral to the city’s na­tional and in­ter­na­tional rep­u­ta­tion. But I’ve of­ten won­dered how much life lies sub­merged, hid­den away from the above-wa­ter pres­sures of Aus­tralia’s big­gest city and its ever-sprawl­ing hu­man pop­u­la­tion. So now I’ve seen proof of the city’s grow­ing rep­u­ta­tion as a sea­horse haven. But what else is veiled from view be­neath the opaque sur­face of the wa­ters near some of our most iconic land­marks, beaches and head­lands?

GEOLOGICALLY, SYD­NEY HAR­BOUR is a river val­ley that was drowned as the sea level rose about 11,000 years ago at the on­set of the present in­ter­glacial pe­riod. But from a ma­rine ecol­ogy per­spec­tive it’s one of the world’s most modif ied es­tu­ar­ine sys­tems. Along with Port Hack­ing, Botany Bay, Pittwa­ter and the Hawkes­bury River, the har­bour is one of a series of deep wa­ter­ways in the Syd­ney Basin that drain along a shal­low coastal strip be­tween Palm Beach and Cronulla.

These wa­ters sup­port habi­tats strongly inf lu­enced by wave en­ergy, wa­ter depth, bot­tom type and salin­ity. Ex­plor­ing them is like swim­ming through sto­ry­book pages filled with a fas­ci­nat­ing cast of colour­ful char­ac­ters.

A series of rocky reefs along Syd­ney’s coast lies sep­a­rated by vast swathes of mo­bile sed­i­ment that with­stand large and pow­er­ful waves. In the shal­lows, these are cov­ered in sea­weed forests (see AG 139) shel­ter­ing com­mon sead­rag­ons feed­ing on swarms of tiny mysid shrimp.

Also here are gi­ant cut­tlef ish, with pig­ment or­gans – chro­matophores – in their skin that change in­stantly, both in colour and tex­ture, to trans­form these be­haviourally com­plex crea­tures from f lam­boy­ant bill­boards to mas­ters of dis­guise. Down in deeper wa­ters, these reefs are cov­ered in a liv­ing ve­neer of colour cre­ated by gar­dens of sponges, as­cid­i­ans and tu­ni­cates in all shapes and sizes.

Blue grop­ers are a re­cur­ring and much-loved part of coastal Syd­ney, famed for their tame be­hav­iour, large size (up to 40kg), blub­bery lips and peg-like teeth. One or two dom­i­nant males are usu­ally in an area, along with sev­eral fe­males. When a male dies or leaves, the largest fe­male changes sex to be­come a re­place­ment male. Many of Syd­ney’s res­i­dent grop­ers have been af­fec­tion­ately named by ador­ing lo­cals – such as Bluey off Clovelly Beach.

Seven aquatic re­serves pro­tect Syd­ney’s most ac­ces­si­ble and bi­o­log­i­cally di­verse coastal ar­eas. Cab­bage Tree Bay Aquatic Re­serve at Manly is one of the most pop­u­lar, where snorkellers can spot south­ern ea­gle rays, dusky whaler sharks and crim­son banded wrasse, all oc­ca­sion­ally swim­ming around dis­carded junk like old mo­tor­bikes.

Within Syd­ney Har­bour’s es­tu­ar­ine en­vi­ron­ments, wa­ters are gen­er­ally shal­lower, more shel­tered and prone to the inf lu­ences of tide and salin­ity. Here, softer sed­i­ments are per­fect habi­tat for bizarre mol­luscs, poly­chaete worms, echin­o­derms and crus­taceans. Three aquatic re­serves also af­ford pro­tec­tion for some of Syd­ney’s es­tu­ar­ine habi­tat at Towra Point in Botany Bay and Shiprock in Port Hack­ing.

Stands of ma­rine veg­e­ta­tion – in­clud­ing man­groves, sea­grass and salt­marsh – pro­vide oases for wad­ing birds such as stilts and pel­i­cans, and habi­tat for ju­ve­nile f ish and ma­rine in­ver­te­brates. Sev­eral species of sea­grass are found in Syd­ney Har­bour, with most at shal­low depths in the outer har­bour. Man­groves are a de­clin­ing habi­tat world­wide, so it’s re­as­sur­ing to learn Syd­ney Har­bour’s man­grove cover has in­creased since Euro­pean set­tle­ment. In con­trast, salt­marsh has fallen dra­mat­i­cally due to fore­shore devel­op­ment. Only an es­ti­mated 37ha re­main.

These days con­sid­er­a­tion of the ma­rine en­vi­ron­ment is now re­quired through the plan­ning and ap­proval process for the in­stal­la­tion of ma­rine in­fra­struc­ture. Devel­op­ments, for ex­am­ple, over ma­rine veg­e­ta­tion are heav­ily reg­u­lated, with sig­nif­i­cant penal­ties for unau­tho­rised harm to aquatic plant species.

IT’S A DARK, SHADOWY world in Syd­ney’s swim­ming en­clo­sures and be­neath jet­ties. Dif­fer­ences in shade, ori­en­ta­tion and wa­ter f low are strong driv­ers of ma­rine plant and an­i­mal life around these ar­ti­fi­cial habi­tats. Such places have proved ben­e­fi­cial for species such as sea­horses, which thrive on swim­ming en­clo­sure nets be­cause they in­crease food and pro­vide refuge from pre­da­tion.

Deep in Syd­ney Har­bour, the calm wa­ters around Chow­der Bay are home to stri­ate an­glerf ish. Per­fectly adapted to the soft sed­i­ment and low-ly­ing sponge habi­tat here, this species has ex­quis­ite cam­ouf lage and uses its f ins like feet to walk along the sea f loor. It also has a built-in lure for at­tract­ing prey and a large mouth to eat them. Com­mon Syd­ney oc­to­puses are here too, their dis­tinc­tive white pupils and rust-coloured arms emerg­ing from lairs un­der rock ledges.

Syd­ney’s ma­rine en­vi­ron­ment is ex­posed to most threats faced glob­ally by coastal ci­ties, in­clud­ing habi­tat loss, fore­shore devel­op­ment, pol­lu­tion, stormwa­ter run-off and in­tro­duced pests. But many plant and an­i­mal in­hab­i­tants ap­pear not only to be cop­ing with the short­com­ings, but find­ing their own strongholds.

Since coastal ecolog ist Pro­fes­sor Peter Stein­berg was ap­pointed Di­rec­tor and Chief Ex­ec­u­tive Of­fi­cer of the Syd­ney In­sti­tute of Ma­rine Sci­ence (SIMS) in 2009, he’s be­come acutely aware of the crit­i­cal role played by an or­gan­i­sa­tion such as his in en­sur­ing the health of Syd­ney’s es­tu­ar­ine and coastal ecosys­tems by pro­vid­ing lo­cal re­search that sup­ports their man­age­ment.

“I get re­minded of the im­por­tance of our work ev­ery time I look out my of­fice win­dow,” he says. “There are peo­ple sail­ing, peo­ple f ish­ing, trans­port ves­sels, cruise ships, not to for­get all of the houses and fore­shore in­fra­struc­ture that line the coast – it’s the per­fect vis­ual for the work we do.”

Hu­man-based threats to and im­pacts on Syd­ney’s wa­ter­ways are re­lent­less and in­creas­ing as more peo­ple are drawn to the city’s wa­ter­ways. “It is ironic that we can po­ten­tially love our wa­ter­ways to their detri­ment,” Peter says, “so at SIMS we are try­ing to un­der­stand what peo­ple think, what they value about the wa­ter­ways and what that means about how you man­age it.”

To ad­dress some ur­ban threats, SIMS re­searchers are now tak­ing steps to­wards prac­ti­cal eco­log­i­cal in­ter­ven­tions to im­prove ex­ist­ing in­fra­struc­ture. “The rea­son is that if we don’t get in there and start do­ing things now, then it might be too late very soon,” Peter ex­plains. “I think there has been a big shift in en­vi­ron­men­tal sci­ence glob­ally to in­ter­ven­tions, and that takes on a whole bunch of forms – from restora­tion ecol­ogy, to re­ha­bil­i­ta­tion ecol­ogy, to green or eco-en­gi­neer­ing.”

Syd­ney Har­bour, for ex­am­ple, is ex­ten­sively modif ied, with more than half the shore­line re­placed by ar­ti­fi­cial struc­tures such as sea­walls, jet­ties and piers. “We ini­tially built struc­tures that didn’t look like nat­u­ral habi­tats, but we can now con­struct things that fa­cil­i­tate nat­u­ral ma­rine com­mu­ni­ties,” Peter says. “We are start­ing to de­ploy pro­to­types and de­signs in Syd­ney Har­bour to bet­ter con­nect the man­made en­vi­ron­ment with the nat­u­ral en­vi­ron­ment.”

An ex­am­ple is de­sign­ing sea­walls with niches and crevices to in­crease coloni­sa­tion by ma­rine species such as sea­weed, oys­ters, f ish and crabs. De­sign of these eco­log­i­cally friendly sea­walls makes them more like nat­u­ral rocky in­ter­tidal ar­eas, with in­creased habi­tat com­plex­ity and a grad­u­ally slop­ing face to dis­si­pate wave ref lec­tion.

“One chal­lenge is try­ing to f ind cost-ef­fec­tive ways of retrof it­ting ex­ist­ing, smooth-sur­faced ver­ti­cal sea­walls that don’t in­te­grate well with the nat­u­ral en­vi­ron­ment,” Peter says. “We’re hav­ing some suc­cess us­ing tiles cre­ated by our col­lab­o­ra­tors with a 3D printer, which can be at­tached to pre-ex­ist­ing sea­walls and al­low us to in­tro­duce com­plex­ity and struc­ture to the sur­face.”

Hav­ing seen pos­i­tive re­sults of SIMS’ work in the Syd­ney area, Peter re­alised the model could be ap­plied to sim­i­lar ur­ban har­bours else­where. The World Har­bour Project (WHP) re­sulted from SIMS-led work and was launched in 2014 at the IUCN World Parks Congress, held in Syd­ney. It be­gan with 14 part­ners and has grown to in­clude 31, a global ini­tia­tive based on the idea that

De­sign of these eco­log­i­cally friendly sea­walls makes them more like nat­u­ral rocky in­ter­tidal ar­eas.

A pair of young ex­plor­ers chase a school of bait­fish trapped in a rock pool by a re­ced­ing tide near Bondi Beach, along one of Aus­tralia’s busiest coast­lines.

As cray­weed forests are re­stored along Syd­ney’s coast, species such as this pink sea urchin and other in­ver­te­brates seek shel­ter in the habi­tat cre­ated by the fronds.

Coastal ecol­o­gist Pro­fes­sor Peter Stein­berg, Syd­ney In­sti­tute of Ma­rine Sci­ence Di­rec­tor and CEO, heads re­search to im­prove man­age­ment of Syd­ney’s ma­rine en­vi­ron­ment.

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