Fiji - Northern Lau (Vanua Balavu / Cicia / Nayau)

Spalding et al. (2001) describe Fiji as an archipelago resting on two fairly shallow geological structures: the Fiji Platform, which carries Viti Levu and Vanua Levu, and the Lau Ridge. The Lau Islands crown the ridge along Fiji's eastern edge, and the Nanuku Channel separates them from the platform. In the northern part of the chain the islands are mostly high and volcanic, carbonate islands take over farther south, and atolls and near-atolls are scattered along its whole length. Among the biggest Lau structures are the Exploring Isles, where Vanua Balavu, a high island, is joined by an extensive eastward barrier reef that encloses several smaller islands; nearer the middle of the chain, the Bukatatanoa Reefs make up a second large barrier-reef complex. Spalding et al. (2001) estimate about 10,020 km² of coral reef for Fiji as a whole, with some 298 scleractinian coral species recorded, and note that research had concentrated around Suva and the Great Astrolabe Reef, leaving much of the country's reef area poorly known. They also report that the bump-headed parrotfish (Bolbometopon) had not been caught in Lau for at least ten years, and that a warming event early in 2000 bleached 50–100% of corals over wide areas of Fiji, down to 30 m, with heavy subsequent mortality.

For the years after 2000, the sources treat Fiji only within regional summaries. Drawing on the 2004 Southwest Pacific assessment, which covered Fiji, Wilkinson (2006) described the region's reefs as generally in good condition despite extensive bleaching in 2000–2002, with some reefs fully recovered and others not. Anderson ranked human activities and cyclones as the greatest threats, followed by crown-of-thorns starfish and disease, and noted that overexploitation and pollution were concentrated near towns and in lagoons. Souter et al. (2021) report that live hard coral cover in the Fiji Islands subregion rose between 2002 and 2008, but that across the Pacific average cover fell from about 37% before 1998 to 31% in 2019, mainly through bleaching, with the sharpest losses between 2015 and 2017.

This region comprises 36 Global Reef Expedition benthic stations around Vanua Balavu, Cicia, Mago, Nayau, Tuvuca, and Vanua Vatu in the northern Lau group of eastern Fiji, plus an island-level marker for Vanua Balavu and a 2 m snorkel site at Nayau, 38 sites in all. They were surveyed between 15 and 26 June 2013, from Vanua Vatu (15 June), Nayau (16), Tuvuca (17), Cicia (18-19), and Mago (20) to Vanua Balavu (21-26 June), the last stops of the Fiji mission. The majority of stations sit on fore-reef terraces, spur-and-groove slopes, and walls, with maximum dive depths up to 32.3 m at FJCC47 (the Nayau snorkel station, with no logged dive, is 2 m deep); among the scuba stations the shallowest dive was 12.2 m at FJCC46. The survey team's notes describe Nayau's stations as shallow fore-reef slopes built up by acroporids with rubble piled at their bases, and FJNA39 as a classic spur-and-groove reef with well-developed coral on the spur tops.

Coral cover ranged from 2.5% at FJVB64 to 67% on the Cicia barrier reef at FJCC46. Cicia, Mago, Nayau, and Vanua Vatu all held 33% to 67% coral, and their reefs are Acropora-led: FJCC45 is a flat-topped coral mountain paved with table Acropora, FJCC48 has an overhanging buttress of plating corals, FJVV37 has tables cantilevered over a spur-and-groove edge, FJMG49 (53%) is an acroporid-dominated Mago slope, and at Tuvuca FJTV42 carries near-continuous staghorn meadows. The Tuvuca wall at FJTV41 is a gorgonian forest rather than a stony-coral reef, and FJCC47 is a low, dense mosaic of small colonies rather than tables.

On Vanua Balavu, 17 of the island's 19 survey stations were below 30% coral, and algae held most of the benthos (83% at FJVB58, 90% at FJVB69). Survey notes there describe cyanobacteria mats, old dead coral, leather corals, and Millepora, plus a Pavona clavus colony at least 10 m across. The steep slope edge at FJVB52 (47%) and the coral-covered rise at FJVB54 (37%) are the exceptions. Only the three Vanua Vatu stations carry a Coral Health Index, 3.50 out of 5. Island-pooled physiological outlier scores ran from 5.00 (no outliers) at Cicia and Tuvuca to 3.89 at Vanua Balavu on a 0-5 scale, and the one colony sampled at FJVB67 was flagged.

The surveys recorded an active crown-of-thorns outbreak on one Cicia reef, with 212 starfish removed (expedition field report), crown-of-thorns predation with large areas of white coral at Mago, Drupella on Nayau Acropora, a bleached Pocillopora damicornis at FJMG51, two bleached colonies at FJTV41, a bleached and a partly bleached pocilloporid at FJNA40, and a partly bleached tagged colony at FJNA38; Anderson's sampling sheet also records sampled colonies 80% or more bleached at FJCC44, FJMG51, FJVB60, FJVB63, and FJVV36 (95% and 90%), and one at 70% at FJVV35. Sightings include a manta ray at FJVB65, spotted eagle rays at FJTV42, a dogtooth tuna at FJVB54, a green turtle at FJVB69, a day octopus at FJMG49, a triton's trumpet at FJVB67, whitetip reef sharks at FJMG51, FJVB52, FJVB55, FJVB61, and FJVV37, a reef shark at FJTV41, and giant clams at FJCC44, FJMG51, FJNA40, FJVV37, and FJVB68.

E vakamacalataki Viti ko Spalding et al. (2001) me dua na yatu yanuyanu e tiko ena rua na yavu vakaveiyaqani e sega ni titobu sara: na Fiji Platform, e tiko kina o Viti Levu kei Vanua Levu, kei na Lau Ridge. Na Yasayasa vaka-Lau e tu e dela ni ridge ena bati ni tokalau i Viti, ka wasea mai na platform ena Nanuku Channel. Ena yasana i vualiku ni yatu e levu na yanuyanu cecere ka vulikano, ka ra tubu cake na yanuyanu ni vatu ni cakau (carbonate) ena yasana i ceva, ka veitawasei tu na atoll kei na vanua e voleka ni atoll ena kena balavu taucoko. Na ka levu duadua e Lau e okati kina na Exploring Isles, e sema kina o Vanua Balavu, e dua na yanuyanu cecere, ena dua na cakau i tuba (barrier reef) e balavu ki na tokalau ka vakavolivolitaka eso na yanuyanu lalai; e voleka ni loma ni yatu, na Bukatatanoa Reefs e dua tale na isoqosoqo levu ni cakau i tuba. E vakatau ko Spalding et al. (2001) ni rauta ni 10,020 km² na cakau i Viti taucoko, e rauta ni 298 na mataqali lase dina (scleractinian) e volai, ka ra kaya ni levu na vakadidike e cakava voleka i Suva kei na Great Astrolabe Reef, ka se sega ni kilai vinaka e levu na cakau ni vanua. Era volaa tale ga ni sega ni tobo e dua na kalia (bump-headed parrotfish, Bolbometopon) e Lau ena 10 na yabaki se sivia, ka dua na katakata ni wasawasa ena itekitekivu ni 2000 a vulavula kina na 50–100% ni lase ena vanua levu i Viti, ka yacova na 30 m, ka mate vakalevu na lase ni oti oya.

Ni oti na 2000, era vakamacalataka ga na ivola o Viti ena ivakalekaleka vakayasana. Ena nona vakayagataka na vakadidike ni Southwest Pacific ena 2004 ka okati kina o Viti, e vakamacalataka ko Wilkinson (2006) ni levu na cakau ni yasana e tiko vinaka ga e dina ga ni a levu na vulavula ni lase ena 2000–2002, eso na cakau e bula tale vakavinaka ka so e sega. E vakatuvaka na cakacaka ni tamata kei na cagilaba me ra leqa levu duadua, ka tarava na crown-of-thorns starfish kei na mate ni lase, ka kaya ni vakayagataki vakasivia kei na dukadukali e vakalevu e voleka ni koro kei na wai e loma ni cakau. E vakaraitaka ko Souter et al. (2021) ni a tubu na ubi ni lase dina bula ena yasana Fiji Islands ena maliwa ni 2002 kei na 2008, ia ena Pasifika taucoko e lutu na ubi mai na rauta ni 37% ni bera na 1998 ki na 31% ena 2019, vakalevu ena vuku ni vulavula ni lase, ka levu duadua na kena lutu ena maliwa ni 2015 kei na 2017.

E tiko ena yasana oqo e 36 na vanua ni vakadidike ni botoni ni cakau (benthic stations) ni Global Reef Expedition e Vanua Balavu, Cicia, Mago, Nayau, Tuvuca kei Vanua Vatu ena yatu i vualiku i Lau ena tokalau i Viti, kei na dua na ivakatakilakila ni yanuyanu ko Vanua Balavu kei na dua na vanua ni qalo vakaruku (snorkel) e 2 m e Nayau, e 38 kece na vanua. A vakadidiketaki ena maliwa ni 15 kei na 26 Jiune 2013, mai Vanua Vatu (15 Jiune), Nayau (16), Tuvuca (17), Cicia (18-19) kei Mago (20) ki Vanua Balavu (21-26 Jiune), na vanua ni muri duadua ni ilakolako i Viti. E levu na vanua ni vakadidike ena ituvatuvu ni cakau i tuba (fore-reef terraces), na taba spur-and-groove kei na bati tu cake (walls), ka na titobu levu duadua ni nuku e yaco ki na 32.3 m e FJCC47 (na vanua ni snorkel e Nayau, e sega ni volai kina e dua na nuku, e 2 m na kena titobu); ena maliwa ni vanua ni scuba, na nuku e sega ni titobu sara e 12.2 m e FJCC46. E vakamacalataka na ivola ni ilawalawa ni vakadidike ni vanua ni vakadidike e Nayau e taba ni cakau i tuba e sega ni titobu e tara ena acroporids, ka vakasoqoni na vatu lalai (rubble) e kena ruku, ka o FJNA39 e dua na cakau spur-and-groove dina, e tiko kina na lase e tubu vinaka e dela ni spurs.

Na ubi ni lase e tekivu mai na 2.5% e FJVB64 ki na 67% ena cakau i tuba i Cicia e FJCC46. O Cicia, Mago, Nayau kei Vanua Vatu e tiko kina na 33% ki na 67% ni lase, ka liu kina na Acropora: o FJCC45 e dua na ulunivanua ni lase e bibi na dela ka ubia na teveli Acropora, o FJCC48 e tiko kina e dua na bati ni lase bebeka e ubia, o FJVV37 e tiko kina na teveli e lako yani e cake ni bati ni spur-and-groove, o FJMG49 (53%) e dua na taba e Mago e liu kina na acroporids, ka e Tuvuca o FJTV42 e tiko kina na veikoro staghorn e voleka ni veitaravi. Na bati tu cake e Tuvuca e FJTV41 e dua na veikau gorgonian ka sega ni cakau ni lase vatu, ka o FJCC47 e dua na mosaic e sega ni cecere ka vavaku ni veimataqali lase lalai ka sega ni teveli.

E Vanua Balavu, e 17 vei ira na 19 na vanua ni vakadidike ni yanuyanu e lailai sobu mai na 30% ni lase, ka levu na botoni e ubia na lumi (83% e FJVB58, 90% e FJVB69). E vakamacalataka kina na ivola ni vakadidike na cyanobacteria, na lase makawa mate, na lase vakakuli (leather corals) kei na Millepora, kei na dua na Pavona clavus e sivia na 10 m na kena rabai. Na bati ni taba titobu e FJVB52 (47%), na dela ni ulu ni cakau e ubia na lase e FJVB54 (37%) era duatani. E tolu ga na vanua ni vakadidike e Vanua Vatu e tiko kina na Coral Health Index, 3.50 mai na 5. Na naba ni duidui vakayago ni yanuyanu taucoko e tekivu mai na 5.00 (sega ni duidui) e Cicia kei Tuvuca ki na 3.89 e Vanua Balavu ena ivakatagedegede 0-5, ka a vakatakilakilataki na dua ga na lase a tauri e FJVB67.

A volaa na vakadidike e dua na tubu levu ni crown-of-thorns e dua na cakau e Cicia, ka 212 na ika lomalagi a kau tani (ripote ni ilakolako), na kana ni crown-of-thorns kei na vanua levu ni lase vulavula e Mago, na Drupella ena Acropora e Nayau, e dua na Pocillopora damicornis e vulavula e FJMG51, e rua na lase vulavula e FJTV41, e dua na pocilloporid e vulavula kei na dua e vulavula vakaiwasewase e FJNA40, kei na dua na lase e vakatakilakilataki e vulavula vakaiwasewase e FJNA38; e volai tale ga ena ivola ni sampling i Anderson na lase a tauri ka 80% se sivia e vulavula e FJCC44, FJMG51, FJVB60, FJVB63 kei FJVV36 (95% kei na 90%), kei na dua e 70% e FJVV35. Na veika e raici e okati kina e dua na manta e FJVB65, na vai (spotted eagle rays) e FJTV42, e dua na dogtooth tuna e FJVB54, e dua na vonu dina e FJVB69, e dua na kuita e FJMG49, e dua na davui (triton's trumpet) e FJVB67, na qio batidua vulavula e FJMG51, FJVB52, FJVB55, FJVB61 kei FJVV37, e dua na qio ni cakau e FJTV41, kei na vasua e FJCC44, FJMG51, FJNA40, FJVV37 kei FJVB68.