Effects of nutrient additions on intertidal seagrass (Zostera muelleri) habitat in Western Port, Victoria, Australia

2007 ◽  
Vol 58 (7) ◽  
pp. 666 ◽  
Author(s):  
Liz Morris ◽  
Gregory Jenkins ◽  
David Hatton ◽  
Timothy Smith
Keyword(s):  
Water Column ◽  
Nutrient Loading ◽  
Late Summer ◽  
Dry Weight ◽  
Nutrient Addition ◽  
Seagrass Habitat ◽  
Gammarid Amphipod ◽  
Faunal Assemblages ◽  
Nutrient Additions ◽  
Intertidal Seagrass

Loss of seagrass habitat in many parts of the world has been attributed to increases in nutrient loading to nearshore areas. The role of excess epiphyte, macroalgal or phytoplankton growth in shading of seagrass leaves and negatively affecting seagrass health is generally agreed to be a prevalent mechanism in seagrass decline worldwide. In the present study nutrient addition experiments were undertaken at three sites in Western Port, Victoria. Nutrients were added to the water column using the controlled release fertiliser Osmocote™ in late summer 2005. The experiments ran for one month at two of the sites (Blind Bight and Hastings) and at the third site (Crib Point) the experiment ran for three months. Control and nutrient addition plots were monitored for concentrations of inorganic nutrients, number of seagrass leaves, seagrass, epiphyte and loose algal biomass and invertebrate faunal assemblages. Nutrient additions had increased ash free dry weight of seagrass leaves and loose algae at two of the three sites studied. There was also an increase in gammarid amphipod densities at the Crib Point site. We consider that Western Port seagrass habitat is sensitive to increased loads of nutrients within the water column with the Blind Bight region most at risk.

scholarly journals Ecosystem Entanglement and the Propagation of Nutrient-Driven Instability

2020 ◽  
Author(s):  
Kevin S. McCann ◽  
A.S MacDougall ◽  
G.F. Fussmann ◽  
C. Bieg ◽  
K. Cazelles ◽  
...  
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Nutrient Loading ◽  
Transport Theory ◽  
Nutrient Addition ◽  
Edible Plant ◽  
Nutrient Additions ◽  
Theoretical Synthesis ◽  
Human Modification ◽  
And Function

ABSTRACTAlmost 50 years ago, Michael Rosenzweig pointed out that nutrient addition can destabilize food webs, leading to loss of species and reduced ecosystem function through the paradox of enrichment. Around the same time, David Tilman demonstrated that increased nutrient loading would also be expected to cause competitive exclusion leading to deleterious changes in food web diversity. While both concepts have greatly illuminated general diversity-stability theory, we currently lack a coherent framework to predict how nutrients influence food web stability across a landscape. This is a vitally important gap in our understanding, given mounting evidence of serious ecological disruption arising from anthropogenic displacement of resources and organisms. Here, we combine contemporary theory on food webs and meta-ecosystems to show that nutrient additions are indeed expected to drive loss in stability and function in human-impacted regions. However, this loss in stability occurs not just from wild oscillations in population abundance, but more frequently from the complete loss of an equilibrium due to edible plant species being competitively excluded. In highly modified landscapes, spatial nutrient transport theory suggests that such instabilities can be amplified over vast distances from the sites of nutrient addition. Consistent with this theoretical synthesis, the empirical frequency of these distant propagating ecosystem imbalances appears to be growing. This synthesis of theory and empirical data suggests that human modification of the Earth’s ecological connectivity is “entangling” once distantly separated ecosystems, causing rapid, expansive, and costly nutrient-driven instabilities over vast areas of the planet. The corollary to this spatial nutrient theory, though -- akin to weak interaction theory from food web networks -- is that slow spatial nutrient pathways can be potent stabilizers by moderating flows across a landscape.

Autumnal nutrient transfers by retranslocation, leaching, and litter fall in a chestnut oak forest in southern Illinois

1982 ◽  
Vol 12 (1) ◽  
pp. 40-51 ◽  
Author(s):  
Nancy L. Ostman ◽  
George T. Weaver
Keyword(s):  
Late Summer ◽  
Dry Weight ◽  
Litter Fall ◽  
Leaf Color ◽  
Southern Illinois ◽  
Foliar Concentrations ◽  
Important Means ◽  
Study Sites ◽  
Free Falling ◽  
Leaf Dry Weight

Retranslocation from leaves was investigated as a means of retaining nutrients in stands of Quercusprinus L. on two sites in southern Illinois, where wind rapidly moves litter downslope. Foliage samples were collected from late summer until leaf fall to describe the trends of leaf dry weight and nutrient concentration (N, K, P, Ca) changes. Free-falling rain and throughfall were collected to estimate foliar leaching. Foliar concentrations of N, K, and P decreased markedly during senescence while Ca concentrations increased. The pattern of concentration change was unique for each element, and the change in N concentration was closely correlated with change in leaf color. For the study sites as a whole, leaf dry weight decreased to 70% of the original value. Of 84.2 kg N/ha in green foliage, only 22.6% was returned to the site as litter. The canopy gained 0.3 kg N/ha (0.4%) from rainfall. The 78.5% N unaccounted for is attributed to retranslocation. Similarly, from 51.4 kg K/ha; 8.2, P; and 47.8, Ca in green foliage, 9.8, 1.3, and 3.3%, respectively, were removed by leaching; 27.4, 43.7, and 85.1% were returned to the site in litter. The remaining 63.0% K, 55.0% P, and 11.5% Ca unaccounted for is attributed to retranslocation. Retranslocation and leaching of nutrients was greater on the site of higher quality. But on both sites it appears that retranslocation is an important means of retaining and conserving N, K, and P countering the effect of annual litter removal.

Overwinter thermal habitat use in lakes by anadromous Arctic char

2018 ◽  
Vol 75 (12) ◽  
pp. 2343-2353 ◽  
Author(s):  
Ingeborg M. Mulder ◽  
Corey J. Morris ◽  
J. Brian Dempson ◽  
Ian A. Fleming ◽  
Michael Power
Keyword(s):  
Habitat Use ◽  
Water Column ◽  
Prey Capture ◽  
Salvelinus Alpinus ◽  
Late Summer ◽  
Arctic Char ◽  
Foraging Efficiency ◽  
Thermal Habitat ◽  
Metabolic Costs ◽  
Seaward Migration

Anadromous Arctic char (Salvelinus alpinus) migrate back to fresh water in late summer to spawn and (or) overwinter. Upon freshwater entry, feeding is reduced or absent, and movement activity is restricted. While the physiological responses to low temperatures (e.g., growth, metabolism) are understood, specifics of the use of thermal habitat for overwintering remains poorly characterized. This study used acoustic and archival telemetry data from two lakes in southern Labrador, Canada, to study thermal habitat use during the ice-covered period. Results showed that lake-dwelling anadromous Arctic char predominantly occupied a narrow range of temperatures (0.5–2 °C) and used cooler temperatures available within the middle and upper water column. Use of the selected temperatures is likely a strategy that lowers metabolic costs and minimizes energy expenditure, preserving stored lipids for overwinter survival and the energetic costs of preparation for seaward migration. As Arctic char are visual feeders, use of the upper water column is also thought to aid foraging efficiency by increasing the likelihood of prey capture.

scholarly journals Diatoms as a paleoproductivity proxy in the NW Iberian coastal upwelling system (NE Atlantic)

2017 ◽  
Vol 14 (5) ◽  
pp. 1165-1179 ◽  
Author(s):  
Diana Zúñiga ◽  
Celia Santos ◽  
María Froján ◽  
Emilia Salgueiro ◽  
Marta M. Rufino ◽  
...  
Keyword(s):  
Water Column ◽  
Surface Sediment ◽  
Sediment Trap ◽  
Coastal Upwelling ◽  
Late Summer ◽  
Early Summer ◽  
Marine Diatom ◽  
Photic Zone ◽  
Upwelling System ◽  
Water Column Stratification

Abstract. The objective of the current work is to improve our understanding of how water column diatom's abundance and assemblage composition is seasonally transferred from the photic zone to seafloor sediments. To address this, we used a dataset derived from water column, sediment trap and surface sediment samples recovered in the NW Iberian coastal upwelling system. Diatom fluxes (2.2 (±5.6) 106 valves m−2 d−1) represented the majority of the siliceous microorganisms sinking out from the photic zone during all studied years and showed seasonal variability. Contrasting results between water column and sediment trap diatom abundances were found during downwelling periods, as shown by the unexpectedly high diatom export signals when diatom-derived primary production achieved their minimum levels. They were principally related to surface sediment remobilization and intense Minho and Douro river discharge that constitute an additional source of particulate matter to the inner continental shelf. In fact, contributions of allochthonous particles to the sinking material were confirmed by the significant increase of both benthic and freshwater diatoms in the sediment trap assemblage. In contrast, we found that most of the living diatom species blooming during highly productive upwelling periods were dissolved during sinking, and only those resistant to dissolution and the Chaetoceros and Leptocylindrus spp. resting spores were susceptible to being exported and buried. Furthermore, Chaetoceros spp. dominate during spring–early summer, when persistent northerly winds lead to the upwelling of nutrient-rich waters on the shelf, while Leptocylindrus spp. appear associated with late-summer upwelling relaxation, characterized by water column stratification and nutrient depletion. These findings evidence that the contributions of these diatom genera to the sediment's total marine diatom assemblage should allow for the reconstruction of different past upwelling regimes.

Boron Deficiency in a Southern Pine Nursery

1982 ◽  
Vol 6 (2) ◽  
pp. 108-112 ◽  
Author(s):  
E. L. Stone ◽  
C. A. Hollis ◽  
E. L. Barnard
Keyword(s):  
Pinus Taeda ◽  
Soil Management ◽  
Late Summer ◽  
Dry Weight ◽  
Height Growth ◽  
Boron Deficiency ◽  
First Year ◽  
Normal Height ◽  
High Calcium ◽  
Pinus Taeda L

Abstract Boron deficiency in seedling loblolly (Pinus taeda L.) and slash pine (Pinus elliotti Engelm.) in a northern Florida nursery was diagnosed by: (1) characteristic damage to shoot tips and buds, including necrosis of only part of the terminal; and (2) boron concentrations as low as only 1.9 ppm (dry weight) in affected tissues. Soil and soil-management features associated with deficiency include extremely low silt and clay contents, organic matter levels of 1 percent or less, lack of boron addition, and high calcium irrigation water leading to soil reactions above pH 6 by late summer. Consequences of deficiency were not limited to the nursery. Damaged seedlings that survived outplanting developed into bushy plants incapable of normal height growth in the first year or two.

scholarly journals Variation in ω-3 and ω-6 Polyunsaturated Fatty Acids Produced by Different Phytoplankton Taxa at Early and Late Growth Phase

Biomolecules ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 559 ◽  
Author(s):  
Sami Taipale ◽  
Elina Peltomaa ◽  
Pauliina Salmi
Keyword(s):  
Fatty Acids ◽  
Polyunsaturated Fatty Acids ◽  
Growth Phase ◽  
Essential Fatty Acids ◽  
Late Summer ◽  
Dry Weight ◽  
Stationary Growth Phase ◽  
Epa And Dha ◽  
Average Proportion ◽  
Aquatic Food

Phytoplankton synthesizes essential ω-3 and ω-6 polyunsaturated fatty acids (PUFA) for consumers in the aquatic food webs. Only certain phytoplankton taxa can synthesize eicosapentaenoic (EPA; 20:5ω3) and docosahexaenoic acid (DHA; 22:6ω3), whereas all phytoplankton taxa can synthesize shorter-chain ω-3 and ω-6 PUFA. Here, we experimentally studied how the proportion, concentration (per DW and cell-specific), and production (µg FA L−1 day−1) of ω-3 and ω-6 PUFA varied among six different phytoplankton main groups (16 freshwater strains) and between exponential and stationary growth phase. EPA and DHA concentrations, as dry weight, were similar among cryptophytes and diatoms. However, Cryptomonas erosa had two–27 times higher EPA and DHA content per cell than the other tested cryptophytes, diatoms, or golden algae. The growth was fastest with diatoms, green algae, and cyanobacteria, resulting in high production of medium chain ω-3 and ω-6 PUFA. Even though the dinoflagellate Peridinium cinctum grew slowly, the content of EPA and DHA per cell was high, resulting in a three- and 40-times higher production rate of EPA and DHA than in cryptophytes or diatoms. However, the production of EPA and DHA was 40 and three times higher in cryptophytes and diatoms than in golden algae (chrysophytes and synyrophytes), respectively. Our results show that phytoplankton taxon explains 56–84% and growth phase explains ~1% of variation in the cell-specific concentration and production of ω-3 and ω-6 PUFA, supporting understanding that certain phytoplankton taxa play major roles in the synthesis of essential fatty acids. Based on the average proportion of PUFA of dry weight during growth, we extrapolated the seasonal availability of PUFA during phytoplankton succession in a clear water lake. This extrapolation demonstrated notable seasonal and interannual variation, the availability of EPA and DHA being prominent in early and late summer, when dinoflagellates or diatoms increased.

scholarly journals Eutrophic water or fertile sediment: which is more important for the growth of invasive aquatic macrophyte Myriophyllum aquaticum?

2018 ◽  
pp. 3 ◽  
Author(s):  
Bingchang Tan ◽  
Hu He ◽  
Jiao Gu ◽  
Kuanyi Li
Keyword(s):  
Water Column ◽  
Nutrient Loading ◽  
Aquatic Macrophyte ◽  
Control Group ◽  
Sediment Type ◽  
Myriophyllum Aquaticum ◽  
Treatment Groups ◽  
Two Factors ◽  
Outdoor Experiment ◽  
Lateral Branches

Invasive macrophyte Myriophyllum aquaticum is capable of assimilating nutrients from both the sediments and the water column. However, which is the major source of nutrients supporting M. aquaticum growth under various nutrient regimes has not been well documented. Here we conducted a two-factorial outdoor experiment (three levels of nutrient loading and two types of sediments) from 23 May to 27 June 2016, to assess M. aquaticum responses to different nutrient levels in the water column and the sediment. Results showed that concentrations of total nitrogen, total phosphorus and chlorophyll a in the water column increased in the treatment groups, but decreased slightly in the control group (nutrient-poor sediment and no nutrient addition). Sediment type had a significant effect on the growth M. aquaticum, while there were no significant effects of nutrient loading levels and the interactions between the two factors. Mean relative growth rate, mean plant height, mean stem diameter, the number of lateral branches and roots in the nutrient-rich sediment treatments were 1.6, 1.2, 1.6, 3.2 and 5.9 folds greater than in the nutrient-poor sediment treatments, respectively. These results suggest that nutrient-rich sediment has a positive effect on the growth of M. aquaticum. This study reveals possible expansion mechanism of the exotic M. aquaticum in China, and may provide valuable information on the ecological restoration of eutrophic freshwaters.

Role of Ecklonia radiata (C. Ag.) J. Agardh in determining trace metal availability in coastal waters. I. Total trace metals

1987 ◽  
Vol 38 (3) ◽  
pp. 307 ◽  
Author(s):  
HW Higgins ◽  
DJ Mackey
Keyword(s):  
Trace Metals ◽  
Metal Binding ◽  
Late Summer ◽  
Dry Weight ◽  
Metal Availability ◽  
Metal Binding Sites ◽  
Accumulation Of Metals ◽  
Concentration Factors

No seasonal variations were found in the concentrations of Zn, Cd, Cu, K, Ca, Mg and Na in the kelp E. radiata collected from the marine-dominated Port Hacking estuary on the east coast of Australia. Concentrations of Fe and Mn were about 60% higher in late summer. The relative distributions of all metals between different kelp tissues, however, showed no seasonal variation. Concentration factors (dry weight basis) for trace metals ranged from 2600 for Cu to 68 000 for Fe. With high biomasses common in macroalgal ecosystems, a large proportion of the non-sediment- bound trace metals can be associated with the macroalgae, which therefore act as substantial buffers for these elements. Metal concentration factors (Y, wet wt basis) were related to oceanic residence times (τ) by the equation log Y = -0.69 logτ + 5.4. The distribution of the aikaii and akaline earth metais (K, Ca, Mg and Na) was relativeiy uniform throughout the various kelp tissues. However, concentrations of Fe, Mn, Zn and Cd were significantly higher in the older extremities (holdfast and eroding tip) than in the meristematic region. Although the holdfast also had higher levels of Cu than the meristem, levels were lower in the eroding tip. The results suggest either a slow net intracellular accumulation of metals with time or an increase in potential metal- binding sites as the extremities senesce. Translocation and elimination of surplus metals through the eroding tip or holdfast was thought not to be important in E. radiata as metal concentrations did not differ between live and dead haptera of the holdfast. Likewise, storage of metals in either the holdfast or eroding tip was considered unlikely because of the constant relative tissue distribution throughout the year and lack of metal mobilization during periods of growth. Pretreatment of kelp tissue with an EDTA wash released about 90% of the total Zn and Cd, 25% of the Cu and 7% of the Fe, suggesting that a large proportion of the total kelp Zn and Cd is associated with the apparent free space (AFS). With rapid exchange between seawater and the AFS, E. radiata is therefore not generally useful as a sentinel accumulator species in pollution studies for assessing long term integrated changes of metals in the water column.

Effects of intertidal seagrass habitat fragmentation on turbulent diffusion and retention time of solutes

2012 ◽  
Vol 64 (11) ◽  
pp. 2471-2479 ◽  
Author(s):  
M. Lara ◽  
G. Peralta ◽  
J.J. Alonso ◽  
E.P. Morris ◽  
V. González-Ortiz ◽  
...  
Keyword(s):  
Habitat Fragmentation ◽  
Retention Time ◽  
Turbulent Diffusion ◽  
Seagrass Habitat ◽  
Intertidal Seagrass
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