scholarly journals Effects of Fine Sediment on Seagrass Meadows: A Case Study of Zostera muelleri in Pāuatahanui Inlet, New Zealand

2020 ◽  
Vol 8 (9) ◽  
pp. 645
Author(s):  
Iñigo Zabarte-Maeztu ◽  
Fleur E. Matheson ◽  
Merilyn Manley-Harris ◽  
Robert J. Davies-Colley ◽  
Megan Oliver ◽  
...  
Keyword(s):  
New Zealand ◽  
Light Exposure ◽  
Soil Depth ◽  
Light Availability ◽  
Fine Sediment ◽  
Ammonium Concentration ◽  
Seagrass Habitat ◽  
Light Climate ◽  
Seagrass Meadows ◽  
Contrasting Habitats

Seagrass meadows are vulnerable to fine sediment (mud) pollution, with impacts usually attributed to reduction in submerged light. Here we tested two non-exclusive hypotheses, that mud particles (<63 µm) impact seagrasses through both (1) the light climate and (2) changes in substrate physico-chemistry. We tested these hypotheses in Pāuatahanui Inlet, New Zealand, by comparing seagrass presence, abundance, and health, together with light climate and substrate physico-chemistry at contrasting habitats where (1) seagrass used to thrive but no longer grows (historical seagrass), (2) seagrass still persists (existing seagrass) and (3) seagrass has been present recently, but not currently (potential seagrass). Historical seagrass substrate had significantly higher mud (35% average), bulk density (1.5 g cm−3), porewater ammonium concentration (65 µM), and a more reduced redox profile (negative redox at only 2 cm soil depth) as well as a lower light availability when submerged compared to other habitats, while total daily light exposure differed little between habitats. This suggests that failure of seagrass to recolonize historical seagrass habitat reflects substrate muddiness and consequent unfavorable rhizosphere conditions. Our results provide evidence for the multi-stressor effects of fine sediment on seagrasses, with substrate suitability for seagrass being detrimentally affected even where light exposure seems sufficient.

scholarly journals Above-below surface interactions mediate effects of seagrass disturbance on meiobenthic diversity, nematode and polychaete trophic structure

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Francisco J. A. Nascimento ◽  
Martin Dahl ◽  
Diana Deyanova ◽  
Liberatus D. Lyimo ◽  
Holly M. Bik ◽  
...  
Keyword(s):  
Community Structure ◽  
Trophic Structure ◽  
High Throughput Sequencing ◽  
Habitat Degradation ◽  
Light Availability ◽  
Ecosystem Functions ◽  
Seagrass Habitat ◽  
In Situ Experiment ◽  
Natural Systems ◽  
Seagrass Meadows

Abstract Ecological interactions between aquatic plants and sediment communities can shape the structure and function of natural systems. Currently, we do not fully understand how seagrass habitat degradation impacts the biodiversity of belowground sediment communities. Here, we evaluated indirect effects of disturbance of seagrass meadows on meiobenthic community composition, with a five-month in situ experiment in a tropical seagrass meadow. Disturbance was created by reducing light availability (two levels of shading), and by mimicking grazing events (two levels) to assess impacts on meiobenthic diversity using high-throughput sequencing of 18S rRNA amplicons. Both shading and simulated grazing had an effect on meiobenthic community structure, mediated by seagrass-associated biotic drivers and sediment abiotic variables. Additionally, shading substantially altered the trophic structure of the nematode community. Our findings show that degradation of seagrass meadows can alter benthic community structure in coastal areas with potential impacts to ecosystem functions mediated by meiobenthos in marine sediments.

Distribution, transformations and recovery of urinary sulphur and sources of plant-available soil sulphur in irrigated pasture soil–plant systems treated with 35sulphur-labelled urine

1994 ◽  
Vol 122 (1) ◽  
pp. 91-105 ◽  
Author(s):  
M. L. Nguyen ◽  
K. M. Goh
Keyword(s):  
New Zealand ◽  
Irrigation Water ◽  
Soil Depth ◽  
Field Capacity ◽  
Hydriodic Acid ◽  
Rooting Zone ◽  
Pasture Soil ◽  
S Uptake ◽  
Loam Soil ◽  
S Model

SUMMARYA field plot experiment of 271 days duration was conducted on New Zealand irrigated pastures, commencing in the summer (January) 1988, on a Templeton silt loam soil (Udic Ustochrept) by applying 35sulphur (35S)-labelled urine (250 μCi/g S with 1300 μg S/ml) to field plots (600 × 600 mm) at a rate equivalent to that normally occurring in sheep urine patches (150 ml/0·03 m2) to investigate the distribution, transformations and recovery of urinary S in pasture soil–plant systems and sources of plant-available soil S as influenced by the available soil moisture at the time of urine application and varying amounts of applied irrigation water. Results obtained showed that c. 55–90% of 35S-labelled urine was incorporated into soil sulphate (SO42−), ester SO42− and carbon (C)-bonded S fractions within the major plant rooting zone (0–300 mm), as early as 27 days after urine application. Hydriodic acid (Hl)-reducible and C-bonded soil S fractions showed no consistent trend of incorporation. On day 271, labelled-S was found in soil SO42−, Hl-reducible S and C-bonded S fractions to a soil depth of 500 mm, indicating that not only SO42− but also organic S fractions from soils and 35S-labelled urine were leached beyond the major rooting zone. A large proportion (c. 59–75%) of 35S-labelled urine was not recovered in pasture soil–plant systems over a 271-day period, presumably due to leaching losses beyond the 0–300 mm soil depth. This estimated leaching loss was comparable to that (75%) predicted using the S model developed by the New Zealand Ministry of Agriculture. The recovery of urinary S in soil–plant systems over a 271-day period was not affected by different amounts of irrigation water applied 7 days after urine application to soil at either 50 or 75% available water holding capacity (AWHC). However, significantly lower S recovery occurred when urinary S was applied to the soil at 25% AWHC than at field capacity, suggesting that urinary S applied at field capacity might not have sufficient time to be adsorbed by soil particles, enter soil micropores or be immobilized by soil micro-organisms. Both soil ester SO42− and calcium phosphate-extractable soil S in urine-treated soils were found to be major S sources for pasture S uptake. Labelled S from 35S-labelled urine accounted for c. 12–47% of total S in pasture herbage.

Forestry affects the abundance of Phormidium-dominated biofilms and the functioning of a New Zealand river ecosystem

2017 ◽  
Vol 68 (9) ◽  
pp. 1741 ◽  
Author(s):  
Ibon Aristi ◽  
Joanne E. Clapcott ◽  
Vicenç Acuña ◽  
Arturo Elosegi ◽  
Holly Mills ◽  
...  
Keyword(s):  
New Zealand ◽  
Ecosystem Functioning ◽  
Fine Sediment ◽  
Economic Effects ◽  
Ecosystem Metabolism ◽  
Health Issues ◽  
River Ecosystem ◽  
Pine Plantation ◽  
Decomposition Rates ◽  
Alkaline Phosphate

Toxic cyanobacterial proliferations in water bodies can cause serious environmental and public health issues, as well as having economic effects. Increased inputs of nutrients and fine sediment caused by forestry have been hypothesised as possible causes of increased Phormidium-dominated proliferations in New Zealand rivers. Little is known about the effect of these proliferations on river ecosystem functioning. In the present study, we evaluated five sites along the Maitai River (New Zealand) differing in pine plantation cover of their catchments. We hypothesised that Phormidium biofilms would trap more sediments and recycle more phosphorus than diatoms, that Phormidium proliferations would increase with forestry cover in the catchment and that the varying abundance of Phormidium would affect river ecosystem functioning. Phormidium did not trap more sediment or recycle more phosphorus (measured as alkaline phosphate activity) than diatom biofilms. However, the cover of Phormidium did increase with the proportion of forestry in the catchment. Organic matter decomposition rates (measured as loss of tensile strength of standard cotton strips) varied very little among sites, whereas river ecosystem metabolism increased with the abundance of Phormidium, especially in the lower part of the river. The results of the present study suggest that pine forestry does promote Phormidium biofilm abundance and affect ecosystem functioning in the Maitai River.

Fluvial transport dynamics in the Rangitikei River (New Zealand) unravelled through single-grain feldspar luminescence

2020 ◽  
Author(s):  
Anne Guyez ◽  
Stephane Bonnet ◽  
Tony Reimann ◽  
Jakob Wallinga
Keyword(s):  
New Zealand ◽  
Light Exposure ◽  
River Sediments ◽  
High Ratio ◽  
Sediment Flux ◽  
Fluvial Terraces ◽  
The Past ◽  
Transport Distance ◽  
Fluvial Transport ◽  
Single Grain

&lt;p&gt;Over the past decades, luminescence has been widely used for dating sedimentary deposits. Several recent publications suggest luminescence signals can also be used to investigate fluvial transport. Here we explore what information luminescence signals yield in past and present sediment dynamics in the Rangitikei River (RR), New Zealand (Bonnet et al., 2019).&lt;/p&gt;&lt;p&gt;We present a dataset of 30 samples from fluvial terraces and modern river sediments of the RR. For each of the samples, we measured pIRIR luminescence signals of 300 individual sand-sized grains of feldspar (Reimann et al., 2012). We interpret results to evaluate differences between past and modern transport conditions, and to infer information on lateral input of bedrock particles in different river sections.&lt;/p&gt;&lt;p&gt;The information obtained from the single-grain analysis is incredibly rich, and requires new metrics for interpretation. To quantify the percentage of grains that were eroded from bedrock (or very old deposits) and re-deposited with minimal light-exposure, we identified grains for which the pIRIR signal is above 85% of full saturation (Wintle, 2006). For grains below this saturation threshold, we used the bootstrapped minimum age model (Galbraith et al.,1999; Cunningham and Wallinga, 2012) to determine the palaeodose, the best estimate of the natural radiation dose received by grains since their last deposition and burial event. For the modern deposits, we interpret the palaeodose to indicate the light-exposure of the best-bleached grains. Thereby, it provides a proxy of fluvial transport distance of the sediment grains.&lt;/p&gt;&lt;p&gt;For the modern river sediments we obtain palaeodoses between 2 and 6 Gy. A decreasing trend in palaeodose downstream suggests that part of the grains are transported through the entire system and are gradually bleached through light exposure during this process. The downstream trend in palaeodose of the RR is influenced by the connection of a major tributary, the Kawhatau River (KR), characterized by higher palaeodoses. Based on the observed trends, we estimate that the KR contributes three times more to modern sediment flux down the confluence than the upstream RR. Moreover, we observe that downstream of the confluence the percentage of saturated grains increase, which implies significant local input of bedrock particles from valley sides.&lt;/p&gt;&lt;p&gt;Data from recent (Holocene) autogenic fluvial terraces were acquired downstream the RR/KR confluence. They show a high to very high ratio of saturated grains (30-70%). We also document a downstream increasing trend of the percentage of saturated grains in these fluvial terraces, much stronger than for modern deposits. The maximum is observed for terraces at elevation of +28/+34 m, with an input of saturated grains that doubles over a distance of 100 km. As a consequence, saturated grains represent up to 70 % of the grain population in the most downstream sample. This implies a stronger lateral input of bedrock particles in the past, during recent incision of the river and a significant contribution of valley walls to the sediment flux of the RR, probably through landslides and/or lateral fluvial erosion.&lt;/p&gt;

Impacts of fine sediment addition to tussock, pasture, dairy and deer farming streams in New Zealand

2006 ◽  
Vol 51 (11) ◽  
pp. 2154-2172 ◽  
Author(s):  
CHRISTOPH D. MATTHAEI ◽  
FLORIAN WELLER ◽  
DAVID W. KELLY ◽  
COLIN R. TOWNSEND
Keyword(s):  
New Zealand ◽  
Fine Sediment ◽  
Sediment Addition ◽  
Pasture Dairy

A late Miocene and early Pliocene upper slope-to-shelf sequence of calcareous fine sediment from the Pacific margin of New Zealand

1984 ◽  
Vol 15 (1) ◽  
pp. 331-342 ◽  
Author(s):  
P. F. Ballance ◽  
M. R. Gregory ◽  
G. W. Gibson ◽  
G. C. H. Chaproniere ◽  
A. P. Kadar ◽  
...  
Keyword(s):  
New Zealand ◽  
Late Miocene ◽  
Fine Sediment ◽  
Early Pliocene ◽  
The Pacific ◽  
Pacific Margin ◽  
Upper Slope

Factors Affecting Buffalobur (Solanum rostratum) Seed Germination and Seedling Emergence

Weed Science ◽  
2009 ◽  
Vol 57 (5) ◽  
pp. 521-525 ◽  
Author(s):  
Shouhui Wei ◽  
Chaoxian Zhang ◽  
Xiangju Li ◽  
Hailan Cui ◽  
Hongjuan Huang ◽  
...  
Keyword(s):  
Seed Germination ◽  
Light Exposure ◽  
Soil Depth ◽  
Seedling Emergence ◽  
Soil Surface ◽  
Distribution Area ◽  
Burial Depth ◽  
Weed Species ◽  
Continuous Darkness ◽  
Invasive Weed

Buffalobur is a noxious and invasive weed species native to North America. The influence of environmental factors on seed germination and seedling emergence of buffalobur were evaluated in laboratory and greenhouse experiments. The germination of buffalobur seeds occurred at temperatures ranging from 12.5 to 45 C, with optimum germination attained between 25 and 35 C. Buffalobur seeds germinated equally well under both a 14-h photoperiod and continuous darkness; however, prolonged light exposure (≥ 16 h) significantly inhibited the seed germination. Buffalobur seed is rather tolerant to low water potential and high salt stress, as germination was 28 and 52% at osmotic potentials of −1.1 MPa and salinity level of 160 mM, respectively. Medium pH has no significant effect on seed germination; germination was greater than 95% over a broad pH range from 3 to 10. Seedling emergence was higher (85%) for seeds buried at a soil depth of 2 cm than for those placed on the soil surface (32%), but no seedlings emerged when burial depth reached 8 cm. Knowledge of germination biology of buffalobur obtained in this study will be useful in predicting the potential distribution area and developing effective management strategies for this species.

scholarly journals Storm fine sediment flux from catchment to estuary, Waitetuna-Raglan Harbour, New Zealand

2010 ◽  
Vol 44 (1) ◽  
pp. 53-76 ◽  
Author(s):  
Lucy A McKergow ◽  
Mark Pritchard ◽  
Alexander H Elliott ◽  
Maurice J Duncan ◽  
Alastair K Senior
Keyword(s):  
New Zealand ◽  
Fine Sediment ◽  
Sediment Flux

Species-specific depth zonation in New Zealand charophytes as a function of light availability

2002 ◽  
Vol 72 (3-4) ◽  
pp. 209-217 ◽  
Author(s):  
Anne-Maree Schwarz ◽  
Mary de Winton ◽  
Ian Hawes
Keyword(s):  
New Zealand ◽  
Light Availability ◽  
Species Specific ◽  
Depth Zonation
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