Enhanced benthic response to upwelling of the Indonesian Throughflow onto the southern shelf of Timor‐Leste, Timor Sea

Abstract

[1] Benthic microbial metabolism and bacterial diagenetic pathways were measured along the southern shelf of Timor-Leste during an upwelling event in the winter SE monsoon season. Vertical profiles of water properties and bottom water nutrient concentrations, and operational ocean modeling showed subsurface upwelling from the Indonesian Throughflow (ITF) along the southern shelf west of longitude 126 25 0 E and surface upwelling at the far eastern end of the shelf. Warm surface waters above the halocline had salinities of 33.6 to 33.9 overlying cooler ITF water with salinities of 34.4 to 34.6. Beneath the zone of subsurface upwelling and stratification, sediment chlorophyll a (range: 2.8-4.4 mg g À1 ) and phaeopigment (range: 4.5-7.0 mg g À1 ) concentrations were sufficient to fuel very rapid rates of benthic oxygen consumption (range: 89.9-142.3 mmol m À2 day À1 ) and dissolved inorganic carbon (DIC) release (range: 108.1-148.9 mmol m À2 day À1 ) across the sediment-water interface, and DIC (range: 94.7-142.5 mmol m À2 day À1 ) and NH 4 + (range: 13.3-19.9 mmol m À2 day À1 ) production from incubated surface (0-10 cm) sediments. Molar ratios of DIC/NH 4 + production were lower (range: 6.6-7.7) in fine-grained sediments under the subsurface upwelling regime than in sandy, possibly scoured sediments under surface upwelling (range: 11.9-21.2) where there was no evidence of benthic enrichment. It is proposed that subsurface upwelling along the widest portions of the shelf stimulates phytoplankton production, leading to deposition of fresh phytodetritus that is rapidly decomposed on the seafloor. These zones of high biological activity may attract and support large populations of pelagic fish and cetaceans that have been caught for centuries along the south coast.

Iron geochemistry in surface sediments of a temperate semi-enclosed bay, North China

“…Hence, parallel extractions using 0.25 M HCl solution were carried out to correct for H þ -promoted Fe(II) dissolution in the acidic hydroxylamine extraction. Hydroxylamine extraction after the correction represented Fe(III) am (Lovley and Phillips, 1987;Alongi et al, 2013).…”

Palaeogeography and voyage modeling indicates early human colonization of Australia was likely from Timor-Roti

“…Currently, seabird colonies on the islands of the Sahul Shelf are sufficiently distant from Timor-Roti that several of the most abundant pelagic species are only occasionally seen in Indonesian waters (Trainor and Soares, 2004;Trainor, 2005a,b;Lavers et al, 2014). Populations of these same pelagic species on the exposed Sahul Banks islands would be close enough to regularly visit the waters off Timor-Roti, drawn in particular by seasonal upwelling off the south coast of Timor (Alongi et al, 2013). These birds would arrive from the south and disappear to the south.…”

Eocene-Oligocene large-scale circulation of the East Asian summer monsoon recorded in neritic carbonates of the proto-South China Sea

“…Additional references are displayed in Supplementary Material S3. All of them are located coastward of deep-water upwelling zones: the Halimeda bioherms from the Kalukalukuang Bank are located in the southern Makassar Strait where upwelling occurs annually during southeast monsoon period (Utama et al, 2017); the mounds from the Miskito channel develop in nutrient rich-waters related to the upwelling of the ocean-scale Carribean Current impinging the steep margin of the Nicaragua shelf (Roberts et al, 1992); the Halimeda algal bioherms from the northern Great Barrier Reef are distributed within a N-S-oriented band located in mid-shelf to outer reef barrier position and appear to develop preferentially in areas where shelf-edge upwelling from the Coral Sea intrudes into the shelf ; finally, Halimeda mounds from the southern Timor Sea occur in nutrient-rich waters subject to upwelling of water from the Indonesian throughflow during winter SE monsoon (Alongi et al, 2013).…”