High sedimentary oxygen consumption indicates that sewage input from small islands drives benthic community shifts on overfished reefs

Ford, Amanda K.; Hoytema, Nanne van; Moore, Bradley R.; Pandihau, Lina; Wild, Christian; Ferse, Sebastian C. A.

doi:10.1017/s0376892917000054

Cited by 25 publications

(20 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…O 2 consumption of sediments is driven by respiration of benthic organisms, microbially-mediated oxidation of OM, and reduced inorganic metabolites ( Kristensen, 2000 ), therefore SOC can indicate OM input and degradation at a local level. In situ determination of SOC was based on methods used by Ford et al (2017) . Sediment cores (10 cm 3 ) were collected from enclosures using cut 50 ml syringes and transferred immediately to 160 ml glass incubation chambers.…”

Section: Methodsmentioning

confidence: 99%

Effects of sandfish (Holothuria scabra) removal on shallow-water sediments in Fiji

Lee

Ford

Mangubhai

et al. 2018

PeerJ

Self Cite

View full text Add to dashboard Cite

Sea cucumbers play an important role in the recycling and remineralization of organic matter (OM) in reef sands through feeding, excretion, and bioturbation processes. Growing demand from Asian markets has driven the overexploitation of these animals globally. The implications of sea cucumber fisheries for shallow coastal ecosystems and their management remain poorly understood. To address this knowledge gap, the current study manipulated densities of Holothuria scabra within enclosures on a reef flat in Fiji, between August 2015 and February 2016, to study the effects of sea cucumber removal on sedimentary function as a biocatalytic filter system. Three treatments were investigated: (i) high density (350 g m−2 wet weight; ca. 15 individuals); (ii) natural density (60 g m−2; ca. 3 individuals); and (iii) exclusion (0 g m−2). Quantity of sediment reworked through ingestion by H. scabra, grain size distribution, O2 penetration depth, and sedimentary oxygen consumption (SOC) were quantified within each treatment. Findings revealed that the natural population of H. scabra at the study site can rework ca. 10,590 kg dry sediment 1,000 m−2 year−1; more than twice the turnover rate recorded for H. atra and Stichopus chloronotus. There was a shift towards finer fraction grains in the high treatment. In the exclusion treatment, the O2 penetration depth decreased by 63% following a 6 °C increase in water temperature over the course of two months, while in the high treatment no such change was observed. SOC rates increased ca. two-fold in the exclusion treatment within the first month, and were consistently higher than in the high treatment. These results suggest that the removal of sea cucumbers can reduce the capacity of sediments to buffer OM pulses, impeding the function and productivity of shallow coastal ecosystems.

show abstract

Section: Methodsmentioning

confidence: 99%

Effects of sandfish (Holothuria scabra) removal on shallow-water sediments in Fiji

Lee

Ford

Mangubhai

et al. 2018

PeerJ

Self Cite

View full text Add to dashboard Cite

show abstract

“…this nutrient can enter tropical reef systems via wastewater discharge, aquaculture, and terrestrial runoff from urbanised and agricultural land (Figure 3). Sewage input for instance can strongly shift the canonical Redfield ratio from 16:1 (N:P) to <10 (Lapointe et al, 2005), and has been linked to proliferation of benthic cyanobacterial mats (Ford et al, 2017). Furthermore, occurrence of mats during the rainy season at a site in Curaçao coincided with N:P ratios dropping from 50 to 16 (Brocke et al, 2015a;den Haan et al, 2016).…”

Section: Factors Promoting Cyanobacterial Mat Proliferation On Reefsmentioning

confidence: 99%

Reefs under Siege—the Rise, Putative Drivers, and Consequences of Benthic Cyanobacterial Mats

et al. 2018

Self Cite

View full text Add to dashboard Cite

Benthic cyanobacteria have commonly been a small but integral component of coral reef ecosystems, fulfilling the critical function of introducing bioavailable nitrogen to an inherently oligotrophic environment. Though surveys may have previously neglected benthic cyanobacteria, or grouped them with more conspicuous benthic groups, emerging evidence strongly indicates that they are becoming increasingly prevalent on reefs worldwide. Some species can form mats comprised by a diverse microbial consortium which allows them to exist across a wide range of environmental conditions. This review evaluates the putative driving factors of increasing benthic cyanobacterial mats, including climate change, declining coastal water quality, iron input, and overexploitation of key consumer and ecosystem engineer species. Ongoing global environmental change can increase growth rates and toxin production of physiologically plastic benthic cyanobacterial mats, placing them at a considerable competitive advantage against reef-building corals. Once established, strong ecological feedbacks [e.g., inhibition of coral recruitment, release of dissolved organic carbon (DOC)] reinforce reef degradation. The review also highlights previously overlooked implications of mat proliferation, which can extend beyond reef health and affect human health and welfare. Though identifying (opportunistic) consumers of mats remains a priority, their perceived low palatability implies that herbivore management alone may be insufficient to control their proliferation and must be accompanied by local measures to improve water quality and watershed management.

show abstract

“…Though in part this observation can be linked to observers being more aware of them, a unique 40-year dataset from the Caribbean showed unequivocally that they have become more dominant in recent years alongside declines in hard corals and other key benthic groups 5 . The factors directly responsible for these changes remain uncertain but decreasing water quality and increasing water temperatures are likely primarily responsible 2 , 6 – 8 . Indeed, cyanobacteria are projected to become more problematic in a variety of aquatic systems in the coming years with increasing climate change-related factors and deteriorating local conditions that favour their growth 9 – 11 .…”

Section: Introductionmentioning

confidence: 99%

First insights into the impacts of benthic cyanobacterial mats on fish herbivory functions on a nearshore coral reef

Ford

Visser

Herk

et al. 2021

Sci Rep

Self Cite

View full text Add to dashboard Cite

Benthic cyanobacterial mats (BCMs) are becoming increasingly common on coral reefs. In Fiji, blooms generally occur in nearshore areas during warm months but some are starting to prevail through cold months. Many fundamental knowledge gaps about BCM proliferation remain, including their composition and how they influence reef processes. This study examined a seasonal BCM bloom occurring in a 17-year-old no-take inshore reef area in Fiji. Surveys quantified the coverage of various BCM-types and estimated the biomass of key herbivorous fish functional groups. Using remote video observations, we compared fish herbivory (bite rates) on substrate covered primarily by BCMs (> 50%) to substrate lacking BCMs (< 10%) and looked for indications of fish (opportunistically) consuming BCMs. Samples of different BCM-types were analysed by microscopy and next-generation amplicon sequencing (16S rRNA). In total, BCMs covered 51 ± 4% (mean ± s.e.m) of the benthos. Herbivorous fish biomass was relatively high (212 ± 36 kg/ha) with good representation across functional groups. Bite rates were significantly reduced on BCM-dominated substratum, and no fish were unambiguously observed consuming BCMs. Seven different BCM-types were identified, with most containing a complex consortium of cyanobacteria. These results provide insight into BCM composition and impacts on inshore Pacific reefs.

show abstract

High sedimentary oxygen consumption indicates that sewage input from small islands drives benthic community shifts on overfished reefs

Cited by 25 publications

References 30 publications

Effects of sandfish (Holothuria scabra) removal on shallow-water sediments in Fiji

Effects of sandfish (Holothuria scabra) removal on shallow-water sediments in Fiji

Reefs under Siege—the Rise, Putative Drivers, and Consequences of Benthic Cyanobacterial Mats

First insights into the impacts of benthic cyanobacterial mats on fish herbivory functions on a nearshore coral reef

Contact Info

Product

Resources

About