Benthic primary production in emerged intertidal habitats provides resilience to high water column turbidity

Drylie, Tarn P.; Lohrer, Andrew M.; Needham, Hazel Rosemary; Bulmer, R.H.; Pilditch, Conrad A.

doi:10.1016/j.seares.2018.09.015

Cited by 35 publications

(27 citation statements)

References 69 publications

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“…Measurements of CO 2 concentration (ppm) were recorded at a frequency of 1 Hz for a total incubation period of 5 min. This method has been shown to provide a reliable quantification of CO 2 exchange in intertidal habitats, with a 5 min period resulting in a stable diffusion of CO 2 without increasing the humidity within the chamber [25,40]. Light incubations were conducted before an opaque shade cloth was placed over the chamber base and allowed to acclimate for 20 min prior to an additional CO 2 incubation performed in dark conditions.…”

Section: Primary Production Measurementsmentioning

confidence: 99%

“…This has been demonstrated in several estuaries throughout the world, where benthic primary productivity is often reported to be limited to low tide periods [21][22][23][24]. The dependence on this exposure period and the relative contribution of low tide MPB production may therefore be closely coupled to site turbidity [25]. Despite this crucial link, there are few studies where direct comparisons of emerged and submerged primary production exist [23,26,27], especially through time and along a transitional gradient of water column turbidity.…”

Section: Introductionmentioning

confidence: 99%

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Water Column Turbidity Not Sediment Nutrient Enrichment Moderates Microphytobenthic Primary Production

Mangan

Lohrer

Thrush

et al. 2020

JMSE

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Soft sediment intertidal habitats are under intense anthropogenic pressure resulting from increased land derived sediment and nutrient delivery. Long term, this can cause high water column turbidity and nutrient enrichment of sediment porewaters, which has cascading effects on coastal ecosystem functionality. However, how these stressors may interact and influence benthic productivity over alternating periods of submergence and emergence is largely unknown. This study investigates the effects of sediment nutrient enrichment (at three levels for 20 months) on benthic primary production at six sites in four New Zealand estuaries that spanned a gradient in water column turbidity. While nutrient enrichment had no detectable effect on microphytobenthic primary production, water column turbidity had a significant influence, explaining up to 40% of variability during tidal submergence, followed by temperature and sediment characteristics. In addition, negative net primary production (NPP) estimates and therefore net heterotrophy for the most turbid estuaries during tidal submergence resulted in an increased reliance on production during emerged periods, where NPP was positive across all sites. This study highlights the prominent role of water column turbidity over nutrient enrichment in moderating microphytobenthic production, and the increasing importance of emerged periods to maintain the health and functioning of coastal habitats.

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Section: Primary Production Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Water Column Turbidity Not Sediment Nutrient Enrichment Moderates Microphytobenthic Primary Production

Mangan

Lohrer

Thrush

et al. 2020

JMSE

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“…As seagrass in this study was intertidal, and was shown to be more productive during tidal emergence at all three sites (Drylie et al, 2018), the access of intertidal seagrass to light during the low tide period (when turbidity is a non-factor) may allow it to persist even at the most highly turbid sites. However, the capacity of seagrass to take up nutrients may be influenced by light climate on a range of time scales.…”

Section: Discussionmentioning

confidence: 70%

Elevated Turbidity and the Nutrient Removal Capacity of Seagrass

et al. 2018

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Seagrass meadows provide a range of important ecosystem functions that can be influenced by anthropogenic pressures. Sediment loading from coastal land use mismanagement can elevate turbidity and reduce seabed light levels, thereby impacting seagrass primary productivity and meadow health. Less understood is the impact of elevated turbidity on the nutrient removal capacity of seagrass, which is a key ecosystem function. Here, we use in situ benthic chambers to show that elevated turbidity is associated with lower nutrient (NH 4 + ) removal within intertidal seagrass meadows. Our results suggest that reductions in sediment loading to improve water clarity may increase the nutrient removal capacity of intertidal seagrass meadows influenced by light limitation. When quantifying important ecosystem functions such as nutrient removal by seagrass it is important to consider this context dependency.

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“…These results suggest that, at least at these study sites, sediments may switch between being a source of CO 2 during tidal www.nature.com/scientificreports www.nature.com/scientificreports/ submergence, to a sink of CO 2 during tidal emergence. This may be due to the higher light intensity available at the surface of the sediment under emerged conditions 11,43 , allowing higher rates of photosynthesis by the microphytobenthos and lower rates of ventilation (meaning lower rates of CO 2 release) by macrofauna such as bivalves under emerged conditions 44 .…”

Section: Discussionmentioning

confidence: 99%

“…1 ). However, key drivers that influence GHG (greenhouse gas) fluxes (specifically CO 2 , CH 4 , and N 2 O) on intertidal flats change significantly between tidal inundation and emergence, such as the benthic light climate 11 , temperature 12 , oxygen dynamics 12,13 , and macrofaunal activity 14,15 . If these drivers result in differences in GHG fluxes between submerged and emerged periods, upscaling from submerged fluxes to the full tidal cycle may result in inaccurate accounting of GHG budgets due to under-or over-estimates.…”

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confidence: 99%

Nitrogen enrichment increases greenhouse gas emissions from emerged intertidal sandflats

Hamilton

Bulmer

Schwendenmann

et al. 2020

Sci Rep

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Unvegetated, intertidal sandflats play a critical role in estuarine carbon and nutrient dynamics. However, these ecosystems are under increasing threat from anthropogenic stressors, especially nitrogen enrichment. While research in this area typically focuses on sediment-water exchanges of carbon and nutrients during tidal inundation, there remain significant gaps in our understanding of GHG (Greenhouse Gas) fluxes during tidal emergence. Here we use in situ benthic chambers to quantify GHG fluxes during tidal emergence and investigate the impact of nitrogen enrichment on these fluxes. Our results demonstrate significant differences in magnitude and direction of GHG fluxes between emerged and submerged flats, demonstrating the importance of considering tidal state when estimating GHG emissions from intertidal flats. These responses were related to differences in microphytobenthic and macrofaunal activity, illustrating the important role of ecology in mediating fluxes from intertidal flats. Our results further demonstrate that nitrogen enrichment of 600 gN m −2 was associated with, on average, a 1.65x increase in CO 2 uptake under light (photosynthetically active) conditions and a 1.35x increase in co 2 emission under dark conditions, a 3.8x increase in CH 4 emission and a 15x increase in n 2 O emission overall. This is particularly significant given the large area intertidal flats cover globally, and their increasing exposure to anthropogenic stressors.

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Benthic primary production in emerged intertidal habitats provides resilience to high water column turbidity

Cited by 35 publications

References 69 publications

Water Column Turbidity Not Sediment Nutrient Enrichment Moderates Microphytobenthic Primary Production

Water Column Turbidity Not Sediment Nutrient Enrichment Moderates Microphytobenthic Primary Production

Elevated Turbidity and the Nutrient Removal Capacity of Seagrass

Nitrogen enrichment increases greenhouse gas emissions from emerged intertidal sandflats

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