Tonga - Niua (TONI56)

Setting

A side-on (intermediate exposure) fringing fore reef on the west coast of Niuatoputapu, in northern Tonga (the Living Oceans Foundation habitat map, the 933-site table, and the survey team's field report; see Notes). The station was surveyed on 29 September 2013 during the Khaled bin Sultan Living Oceans Foundation's Global Reef Expedition to Tonga; Anderson's sampling sheet lists it that day with none of the target Pocillopora found ('no Pdam').

General benthic features

Porites was the most common coral genus on this station's transects (13% of the benthos), followed by Montipora (7.1%), Acropora (4.5%), Pocillopora (4.1%), Astreopora (4.0%), and Turbinaria (2.7%). Alongside the hard coral already reported for this site, the same transects recorded 30% crustose coralline algae, 8.1% turf, 6.6% macroalgae, and 2.2% cyanobacteria. Non-living substrate came to 39% pavement, 4.3% dead coral, 6.5% rubble, and 6.5% sand.

Coral cover

• Reference: Khaled bin Sultan Living Oceans Foundation, Global Reef Expedition (in situ transect)
• The expedition's benthic transects recorded 44% hard coral cover (LOF-GRE in situ transects; mean of all of this station's own transects) — a diver transect measurement, not a photographic or computer vision estimate.
• Transect mean 44 ± 2.3% SE (n = 5 transects; Living Oceans Foundation per-transect benthic data); the headline above is this all-transect mean.

Stressors

The survey team's site notes record that many Astreopora had small dead areas, which formed a chimney with tufts of red algae, and that 10-20% of the Pocillopora were sick (Khaled bin Sultan Living Oceans Foundation expedition site notes, 2013). The Living Oceans Foundation transects here recorded 2.2% cyanobacteria and no recently dead coral; they carry no bleaching, disease, or crown-of-thorns field.

Fish and other fauna

Paired fish transects recorded about 18 fish species per transect and about 2.6 kg per 100 m2 of biomass.

Comparisons with other data

No Reef Check station lies within 5 km of this station. The closest Reef Check site, The Coral Gardens, in Vava'u, is about 310 km away; its only survey, on 8 July 2013, recorded 59% hard coral (one 12 m transect; Reef Check data, a different reef, not a survey of this station).

Other notes

Field terms: the survey team's field report opens 'Fringing reef on the west coast'; Anderson's sampling sheet (LOF fellowship 2016 workbook) gives 'leeward', 'forereef', 'fringing reef'; the 933-site table lists an 'intermediate' fringing reef on the fore reef. The Living Oceans Foundation habitat map places the pin on 'shallow fore reef slope', facing southwest, 95-98 degrees off the prevailing trade winds, which makes it side-on; the map and the 933-site table agree. Trade-wind reference: east-southeast trades, about 120 degrees (under 60 degrees off = windward, over 120 = leeward, between = side-on). No photographs exist for this station.

Survey team's site notes: Fringing reef on the west coast. This area had relatively low relief mounds surrounded by sand and rubble. There is a long ridge, 2-3 m wide and 2 m above the surrounding rubble/sand that slopes gradually from 8-15 m. Reef had moderately high cover with 30-50% at 12-15 m dropping to 20-40% at 20 m. It was dominated by 50-100 cm Porites, Astreopora, Montipora, Turbinaria, and Pocillopora. There were very few acroporids except some staghorn corals on the ridge and a large stand of Isopora at the deeper end of the ridge. Small patches of Halimeda occurred throughout the area. Turf ranged from 30-50% being densest in damselfish lawns. There were very high numbers of white Linckia, numerous large giant clams, and dozens of spider conch.