Long-term changes in kelp forests in an inner basin of the Salish Sea

Kelp forests form an important biogenic habitat that responds to natural and human drivers. Global concerns exist about threats to kelp forests, yet long-term information is limited and research suggests that trends are geographically distinct. We examined distribution of the bull kelp Nereocystis luetkeana over 145 years in South Puget Sound (SPS), a semi-protected inner basin in a fjord estuary complex in the northeast Pacific Ocean. We synthesized 48 historical and modern Nereocystis surveys and examined presence/absence within 1-km segments along 452 km of shoreline. Compared to the earliest baseline in 1878, Nereocystis extent in 2017 decreased 63%, with individual sub-basins showing up to 96% loss. Losses have persisted for decades, across a range of climate conditions. In recent decades, Nereocystis predominantly occurred along shorelines with intense currents and mixing, where temperature and nutrient concentrations did not reach thresholds for impacts to Nereocystis performance, and high current speeds likely excluded grazers. Losses predominated in areas with elevated temperature, lower nutrient concentrations, and relatively low current velocities. The pattern of long-term losses in SPS contrasts with stability in floating kelp abundance during the last century in an area of the Salish Sea with greater wave exposure and proximity to oceanic conditions. These findings support the hypothesis that kelp beds along wave-sheltered shorelines exhibit greater sensitivity to environmental stressors. Additionally, shorelines with strong currents and deep-water mixing may provide refugia within sheltered systems.

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Long-term changes in kelp forests in an inner basin of the Salish Sea

10.1101/2020.02.13.947309 ◽

2020 ◽

Cited By ~ 1

Author(s):

Helen D. Berry ◽

Thomas F. Mumford ◽

Bart Christiaen ◽

Pete Dowty ◽

Max Calloway ◽

...

Keyword(s):

Human Impacts ◽

Recent Observation ◽

Puget Sound ◽

Kelp Forests ◽

Limited Data ◽

Biogenic Habitat ◽

Conservation Actions ◽

Almost All ◽

Insight Into

AbstractUnderstanding the historical extent of biogenic habitats can provide insight into the nature of human impacts and inform restoration and conservation actions. Kelp forests form an important biogenic habitat that responds to natural and human drivers. Global concerns exist about threats to kelp forests, yet long term information is limited and research suggests that trends are geographically distinct. We examined distribution of the bull kelp Nereocystis luetkeana over 145 years in South Puget Sound (SPS), a semi-protected inner basin in a fjord estuary complex in the northeast Pacific Ocean. We synthesized 48 historical and modern Nereocystis surveys and examined presence/absence within 1-km shoreline segments along 452 km of shoreline. Over the last 145 years, Nereocystis has been documented in 26% of the shoreline segments. Its extent decreased 62% basin-wide between the 1870s and 2017, with extreme losses in the two out of three sub-basins (96% in Central and 83% in West). In recent years, almost all Nereocystis occurred in the East sub-basin. In the majority of segments where Nereocystis disappeared, the most recent observation was 4 decades ago, or earlier. Multiple natural and human factors that are known to impact kelp could have contributed to observed patterns, but limited data exist at the spatial and temporal scale of this study. In some areas, recent environmental conditions approached thresholds associated with decreased kelp performance. Longstanding Nereocystis losses occurred exclusively in areas with relatively low current velocities. Remaining Nereocystis predominantly occurred in areas where circulation is stronger. Exceptions to this pattern demonstrate that additional factors outside the scope of this study contributed to trajectories of Nereocystis persistence or loss.

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The role of kelp crabs as consumers in bull kelp forests—evidence from laboratory feeding trials and field enclosures

PeerJ ◽

10.7717/peerj.3372 ◽

2017 ◽

Vol 5 ◽

pp. e3372 ◽

Cited By ~ 4

Author(s):

Katie Dobkowski

Keyword(s):

Feeding Preference ◽

Kelp Forests ◽

Feeding Rates ◽

Salish Sea ◽

Growth And Survival ◽

Kelp Beds ◽

San Juan Islands ◽

Feeding Experiments ◽

Feeding Trials ◽

Ne Pacific

The Northern kelp crab (Pugettia producta) and the graceful kelp crab (Pugettia gracilis) are common primary consumers in bull kelp beds near the San Juan Islands (Salish Sea, NE Pacific). In this system, urchins (often considered the most voracious herbivores exerting top-down control on kelp beds) tend to remain sedentary because of the high availability of detrital macroalgae, but the extent to which kelp crabs consume kelp (and other food options) is largely unknown. I conducted four types of laboratory feeding experiments to evaluate kelp crab feeding patterns: (1) feeding electivity between bull kelp (Nereocystis luetkeana) and seven species of co-occurring local macroalgae; (2) feeding electivity on aged vs. fresh bull kelp; (3) feeding preference between N. luetkeana and small snails (Lacuna sp.); and (4) scaling of feeding rate with body size in P. producta and P. gracilis. In choice experiments, P. producta consumed greater mass of N. luetkeana than of other macroalgal species offered and elected to eat fresh bull kelp over aged. However, P. producta also consumed snails (Lacuna sp.), indicating more generalized feeding than previously suspected. Feeding rates for P. producta exceeded the expected 3∕4 scaling rule of metabolic rates, indicating that larger P. producta may have a disproportionately large impact on bull kelp. A subtidal field experiment, designed to assess the influence of consumers on juvenile bull kelp net tissue gain, found that only fully enclosed (protected) bull kelp increased in wet mass and blade length. Herbivory by kelp crabs, among other consumers, is likely to play a previously unrecognized role in mediating the growth and survival of this annual kelp species within the Salish Sea.

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Long-term estimation of the canopy photosynthesis of a leafy vegetable based on greenhouse climate conditions and nadir photographs

Scientia Horticulturae ◽

10.1016/j.scienta.2021.110433 ◽

2021 ◽

Vol 289 ◽

pp. 110433

Author(s):

Koichi Nomura ◽

Daisuke Yasutake ◽

Takahiro Kaneko ◽

Tadashige Iwao ◽

Takashi Okayasu ◽

...

Keyword(s):

Leafy Vegetable ◽

Canopy Photosynthesis ◽

Climate Conditions ◽

Greenhouse Climate

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Bacterial Communities and Enzymatic Activities in Sediments of Long-Term Fish and Crab Aquaculture Ponds

Microorganisms ◽

10.3390/microorganisms9030501 ◽

2021 ◽

Vol 9 (3) ◽

pp. 501

Author(s):

Zhimin Zhang ◽

Qinghui Deng ◽

Lingling Wan ◽

Xiuyun Cao ◽

Yiyong Zhou ◽

...

Keyword(s):

Bacterial Communities ◽

Enzymatic Activities ◽

Nutrient Concentrations ◽

Biological Processes ◽

Farming Practices ◽

Mitten Crab ◽

Aquaculture Ponds ◽

Pond Sediments ◽

Sediment Ph

Aquaculture is among the most important and fastest growing agriculture sectors worldwide; however, it generates environmental impacts by introducing nutrient accumulations in ponds, which are possibly different and further result in complex biological processes in the sediments based on diverse farming practices. In this study, we investigated the effects of long-term farming practices of representative aquatic animals dominated by grass carp (GC, Ctenopharyngodon idella) or Chinese mitten crab (CMC, Eriocheir sinensis) on the bacterial community and enzyme activity of sediments from more than 15 years of aquaculture ponds, and the differences associated with sediment properties were explored in the two farming practices. Compared to CMC ponds, GC ponds had lower contents of TC, TN, and TP in sediments, and similar trends for sediment pH and moisture content. Sediment bacterial communities were significantly different between GC and CMC ponds, with higher bacterial richness and diversity in GC ponds. The bacterial communities among the pond sediments were closely associated with sediment pH, TC, and TN. Additionally, the results showed profoundly lower activities of β-1,4-glucosidase, leucine aminopeptidase, and phosphatase in the sediments of GC ponds than CMC ponds. Pearson’s correlation analysis further revealed strong positive correlations between the hydrolytic enzyme activities and nutrient concentrations among the aquaculture ponds, indicating microbial enzyme regulation response to sediment nutrient dynamics. Our study herein reveals that farming practices of fish and crab differently affect bacterial communities and enzymatic activities in pond sediments, suggesting nutrient-driven sediment biological processes in aquaculture ponds for different farming practices.

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Contextualizing Autophagy during Gametogenesis and Preimplantation Embryonic Development

International Journal of Molecular Sciences ◽

10.3390/ijms22126313 ◽

2021 ◽

Vol 22 (12) ◽

pp. 6313

Author(s):

Marcelo T. Moura ◽

Laís B. Latorraca ◽

Fabíola F. Paula-Lopes

Keyword(s):

Embryonic Development ◽

Germ Cells ◽

Physiological Role ◽

Degradation Pathway ◽

Environmental Stressors ◽

Preimplantation Embryos ◽

Environmental Cues ◽

Term Survival ◽

Assisted Reproduction Technologies

Mammals face environmental stressors throughout their lifespan, which may jeopardize cellular homeostasis. Hence, these organisms have acquired mechanisms to cope with stressors by sensing, repairing the damage, and reallocating resources to increase the odds of long-term survival. Autophagy is a pro-survival lysosome-mediated cytoplasm degradation pathway for organelle and macromolecule recycling. Furthermore, autophagy efflux increases, and this pathway becomes idiosyncratic depending upon developmental and environmental contexts. Mammalian germ cells and preimplantation embryos are attractive models for dissecting autophagy due to their metastable phenotypes during differentiation and exposure to varying environmental cues. The aim of this review is to explore autophagy during mammalian gametogenesis, fertilization and preimplantation embryonic development by contemplating its physiological role during development, under key stressors, and within the scope of assisted reproduction technologies.

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Nutrient cycling differs between cropped soils with century-old and recently pyrolyzed biochar

10.5194/egusphere-egu21-15676 ◽

2021 ◽

Author(s):

Victor Burgeon ◽

Julien Fouché ◽

Sarah Garré ◽

Ramin Heidarian-Dehkordi ◽

Gilles Colinet ◽

...

Keyword(s):

Nutrient Cycling ◽

Soil Solution ◽

Nutrient Dynamics ◽

Chemical Properties ◽

Crop Productivity ◽

Nutrient Concentrations ◽

Soil Productivity ◽

Long Term Effects ◽

Mitigation And Adaptation

The amendment of biochar to soils is often considered for its potential as a climate change mitigation and adaptation tool through agriculture. Its presence in tropical agroecosystems has been reported to positively impact soil productivity whilst successfully storing C on the short&#8201;and long-term. In temperate systems, recent research showed limited to no effect on productivity following recent biochar addition to soils. Its long-term effects on productivity and nutrient cycling have, however, been overlooked yet are essential before the use of biochar can be generalized.Our study was set up in a conventionally cropped field, containing relict charcoal kiln sites used as a model for century old biochar (CoBC, ~220 years old). These sites were compared to soils amended with recently pyrolyzed biochar (YBC) and biochar free soils (REF) to study nutrient dynamics in the soil-water-plant system. Our research focused on soil chemical properties, crop nutrient uptake and soil solution nutrient concentrations. Crop plant samples were collected over three consecutive land occupations (chicory, winter wheat and a cover crop) and soil solutions gathered through the use of suctions cups inserted in different horizons of the studied Luvisol throughout the field.Our results showed that YBC mainly influenced the soil solution composition whereas CoBC mainly impacted the total and plant available soil nutrient content. In soils with YBC, our results showed lower nitrate and potassium concentrations in subsoil horizons, suggesting a decreased leaching, and higher phosphate concentrations in topsoil horizons. With time and the oxidation of biochar particles, our results reported higher total soil N, available K and Ca in the topsoil horizon when compared to REF, whereas available P was significantly smaller. Although significant changes occurred in terms of plant available nutrient contents and soil solution nutrient concentrations, this did not transcend in variations in crop productivity between soils for neither of the studied crops. Overall, our study highlights that young or aged biochar behave as two distinct products in terms of nutrient cycling in soils. As such the sustainability of these soils differ and their management must therefore evolve with time.

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Press- and shrink-fit connections with cylindrical aluminum conductors for high-current applications — Contact- and long-term behavior depending on mechanical parameters

2017 IEEE Holm Conference on Electrical Contacts ◽

10.1109/holm.2017.8088099 ◽

2017 ◽

Author(s):

Alexander Ramonat ◽

Stephan Schlegel ◽

Steffen Grossmann ◽

Matthias Kudoke

Keyword(s):

Mechanical Parameters ◽

High Current ◽

Shrink Fit ◽

Long Term Behavior

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Long-term changes of the ice regime of rivers in Latvia

Hydrology Research ◽

10.2166/nh.2016.012 ◽

2016 ◽

Vol 47 (4) ◽

pp. 782-798

Author(s):

Inese Latkovska ◽

Elga Apsīte ◽

Didzis Elferts

Keyword(s):

Regional Differences ◽

Severity Index ◽

Ice Cover ◽

Ice Thickness ◽

Positive Trend ◽

The West ◽

Climate Conditions ◽

Long Term Changes ◽

Ice Regime

The ice regime of rivers is considered a sensitive indicator of climate change. This paper summarises the results of research on the long-term changes in the ice regime parameters under changing climate conditions and their regional peculiarities in Latvia from 1945 to 2012. The ice cover duration on Latvian rivers has decreased during recent decades. The research results demonstrated that there is a positive trend as regards the formation of the ice cover and in 31.8% of the cases the trend is statistically significant at p < 0.05. As regards the breaking up of ice, there is a statistically significant negative trend in 93.2% of the cases at p < 0.05. This indicates an earlier ice break-up date, which in turn, displays a strong correlation with the increase of the air temperature. The same pattern applies to the reduction of the length of ice cover (a statistically significant trend in 86.4% of the cases at p < 0.05). In approximately 60% of the cases, there is a statistically significant reduction of the ice thickness. The estimated winter severity index indicates warmer winters over the last 20 years as well as regional differences in the west–east direction.

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