Periphyton Responses to Higher Trophic Levels and Light in a Shaded Stream

The effects of higher trophic levels on benthic primary producers were examined in the context of light limitation in a shaded headwater stream. Abundance (presence or absence) of a predatory fish Semotilus atromaculatus and a grazing snail Elimia clavaeformis were manipulated with in situ Plexiglas channels, while spatial variability in ambient light was related to variability in primary productivity among channels. Indirect effects of fish on periphyton were insignificant, possibly because grazers that are vulnerable to fish predation were scarce during the experiment, or because fish preyed upon other predators of grazers. Snails had compensatory effects within the periphyton: they diminished biomass and productivity in the loosely attached layer, but stimulated productivity in the tightly attached layer. Snails appeared to mitigate shading of the tightly attached layer by the loosely attached layer. Benthic primary productivity was highly correlated with ambient light levels, accounting for 42% of the variability in total (loosely and tightly attached layers combined) primary productivity. Multiple regression analysis indicated that fish and snail effects on total primary productivity were minor compared to light effects. These results suggest that light availability controls realized as well as potential production in this unproductive stream.

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Role of Predatory Fish in Community Dynamics of an Ephemeral Stream

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f92-255 ◽

1992 ◽

Vol 49 (11) ◽

pp. 2322-2330 ◽

Cited By ~ 18

Author(s):

Joseph R. Holomuzki ◽

R. Jan Stevenson

Keyword(s):

Community Dynamics ◽

Structural Complexity ◽

Benthic Algae ◽

Fish Predation ◽

Trophic Levels ◽

Predatory Fish ◽

Functional Feeding Groups ◽

Ephemeral Stream ◽

Surface Exchange ◽

Invertebrate Predators

In enclosed runs in a third-order ephemeral stream in west-central Kentucky, the effects of predatory sunfish (Lepomis) on benthic macroinvertebrates, benthic algae, and detritivory were compared (1) before stream intermittence, (2) after stream intermittence when transport was restricted, and (3) between substrata offering differential cover from fish predation. Ambient fish densities had little effect on total macrobenthic densities and processes on lower trophic levels before intermittence. Fish modestly affected macroinvertebrate densities after intermittence, when surface exchange of prey was interrupted by sections of dry stream. Among substrata, fish influenced macroinvertebrates on bedrock, but not on stony, coarse substrata. Densities of two taxa were significantly affected by fish, and this significantly altered the relative abundance of functional feeding groups in enclosures on bedrock by increasing the proportion of invertebrate predators in fish treatments. Macroinvertebrate densities in microhabitats on both substrata were not affected by fish presence. Dense growths of the stalked diatom Cymbella generally covered microhabitats and added structural complexity, particularly to bedrock surfaces. Unobstructed, natural migration of prey in the large (40 m2) fencelike enclosures (versus containers), ample refuge space, and low natural densities of fish were important in minimizing fish effects in enclosures.

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Growth Interruptions in Arctic Rhodoliths Correspond to Water Depth and Rhodolith Morphology

Minerals ◽

10.3390/min11050538 ◽

2021 ◽

Vol 11 (5) ◽

pp. 538

Author(s):

Moritz Schlüter ◽

Ines Pyko ◽

Max Wisshak ◽

Christian Schulbert ◽

Sebastian Teichert

Keyword(s):

Light Availability ◽

Growth Patterns ◽

Skeletal Growth ◽

Coralline Algae ◽

Ambient Light ◽

Micro Computed Tomography ◽

Svalbard Archipelago ◽

X Ray ◽

Algal Thalli ◽

Environmental Proxies

Coralline algae that form rhodoliths are widespread globally and their skeletal growth patterns have been used as (paleo-) environmental proxies in a variety of studies. However, growth interruptions (hiati) within their calcareous skeletons are regarded as problematic in this context. Here we investigated how hiati in the growth of Arctic rhodoliths from the Svalbard archipelago correspond to their environment and morphology. Using X-ray micro-computed tomography and stepwise model selections, we found that rhodoliths from deeper waters are subject to more frequent hiatus formation. In addition, rhodoliths with a higher sphericity (i.e., roundness) are less often affected by such growth interruptions. We conclude that these correlations are mainly regulated by hydrodynamics, because, in deeper waters, rhodoliths are not turned frequently enough to prevent a dieback of coralline algal thalli forming on the underside of the rhodolith. In this coherence, spheroidal rhodoliths are turned more easily, therefore shortening the amount of time between turnover events. Moreover, the incidence of light is more advantageous in shallower waters where rhodoliths exhibit a greater share of their surface to diffused ambient light, thus enabling thallus growth also on the down-facing surface of the rhodoliths. In consequence, information on the frequency of hiatus formation combined with rhodolith morphology might serve as a valuable proxy for (paleo-)environmental reconstructions in respect to light availability and the hydrodynamic regime.

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Mechanisms of northern North Atlantic biomass variability

Biogeosciences ◽

10.5194/bg-15-6049-2018 ◽

2018 ◽

Vol 15 (20) ◽

pp. 6049-6066 ◽

Cited By ~ 1

Author(s):

Galen A. McKinley ◽

Alexis L. Ritzer ◽

Nicole S. Lovenduski

Keyword(s):

North Atlantic ◽

North Atlantic Ocean ◽

Light Availability ◽

Light Limitation ◽

Climate Indices ◽

Biogeochemical Model ◽

Full Time ◽

Subpolar Gyre ◽

Phosphate Supply ◽

Biomass Variability

Abstract. In the North Atlantic Ocean north of 40∘ N, intense biological productivity occurs to form the base of a highly productive marine food web. SeaWiFS satellite observations indicate trends of biomass in this region over 1998–2007. Significant biomass increases occur in the northwest subpolar gyre and there are simultaneous significant declines to the east of 30–35∘ W. These short-term changes, attributable to internal variability, offer an opportunity to explore the mechanisms of the coupled physical–biogeochemical system. We use a regional biogeochemical model that captures the observed changes for this exploration. Biomass increases in the northwest are due to a weakening of the subpolar gyre and associated shoaling of mixed layers that relieves light limitation. Biomass declines to the east of 30–35∘ W are due to reduced horizontal convergence of phosphate. This reduced convergence is attributable to declines in vertical phosphate supply in the regions of deepest winter mixing that lie to the west of 30–35∘ W. Over the full time frame of the model experiment, 1949–2009, variability of both horizontal and vertical phosphate supply drive variability in biomass on the northeastern flank of the subtropical gyre. In the northeast subpolar gyre horizontal fluxes drive biomass variability for both time frames. Though physically driven changes in nutrient supply or light availability are the ultimate drivers of biomass changes, clear mechanistic links between biomass and standard physical variables or climate indices remain largely elusive.

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Is thermal stability a factor that influences environmental heterogeneity and phytoplankton distribution in tropical lakes?

Acta Limnologica Brasiliensia ◽

10.1590/s2179-975x8817 ◽

2018 ◽

Vol 30 (0) ◽

Author(s):

Luciana Gomes Barbosa ◽

Francisco Antônio Rodrigues Barbosa ◽

Carlos Eduardo de Mattos Bicudo

Keyword(s):

Thermal Stability ◽

Functional Groups ◽

Environmental Heterogeneity ◽

Driving Forces ◽

Light Availability ◽

Climatic Conditions ◽

Tropical Lakes ◽

Light Limitation ◽

Water Column Stability ◽

Vertical Heterogeneity

Abstract Aim To evaluate the effects of environmental heterogeneity promoted by thermal stratification on the distribution of limnologic variables and phytoplankton functional groups (FGs) in two natural lakes. Methods Monthly measurements were performed over a five-year period in the vertical profile of a warm monomitic shallow lake (Lago Carioca) and in a deep and meromictic (Lake Dom Helvécio). Results The vertical zonation generated by the high thermal stability during the stratification period promoted an increase in the spatial heterogeneity and, consequently, in the richness of functional groups of the two lakes. In the epilimnion, the dominance of small chlorophytes and desmids (NA, A and X1, ≤20μm) and larger dinophyceans (Lo, ≥20μm) were associated with high turbulence and light availability and soluble phosphorus limitation. In the metalimnion, the presence of filamentous cyanobacteria (R) and colonial chlorophyceans (F) of larger size (≥20µm) were associated with stable habitats with high concentrations of N-NH4 and P-PO4-3 and light limiting conditions. Comparatively, Lake Dom Helvécio presented a higher richness of FGs in the meta-hipolimnetic layers (SN, P) as well as a higher number of species per functional group. Seasonal changes in the climatic conditions (e.g. the decrease in air temperature with the consequent heat loss) caused the break of the water column stability, which promoted the redistribution of the dissolved nutrient forms and the increase of light limitation in the two lakes during the mixing period. Therefore, there was a drastic reduction in the richness and population biomass of FGs (≤80%). Conclusions Thermal stability and atelomixis were the main driving forces of vertical heterogeneity during the stratification, favoring the coexistence of FGs and, consequently, their increase in richness and biomass.

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The Lake Ontario Life Support System

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f87-274 ◽

1987 ◽

Vol 44 (12) ◽

pp. 2230-2240 ◽

Cited By ~ 28

Author(s):

D. R. S. Lean ◽

H-J. Fricker ◽

M. N. Charlton ◽

R. L. Cuhel ◽

F. R. Pick

Keyword(s):

Primary Productivity ◽

Life Support ◽

Lake Ontario ◽

Trophic Levels ◽

Phosphorus Concentration ◽

Nutrient Regeneration ◽

Particulate Carbon ◽

Calcium Carbonate Precipitation ◽

Mixing Processes ◽

Aquatic Food

Primary productivity provides most of the energy to support aquatic food chains. The rate is not only influenced by available solar radiation but also by temperature, availability of phosphorus, and the influence of physical mixing processes. The special features of Lake Ontario such as changes in phosphorus concentration, calcium carbonate precipitation, and silica deficiency on primary productivity, concentration of particulate carbon, and chlorophyll are discussed. Our lack of understanding of food chain and nutrient regeneration processes is illustrated through our failure to balance carbon production with losses through zooplankton grazing and sedimentation. It was demonstrated, however, that bacteria are not responsible for nutrient regeneration through "mineralization" but nutrients are effectively recycled in the water column at the second and third trophic levels.

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Effects of juvenile fish predation (Cyprinus carpio L.) on the composition and diversity of free-living freshwater nematode assemblages

Nematology ◽

10.1163/15685411-00002941 ◽

2016 ◽

Vol 18 (1) ◽

pp. 39-52 ◽

Cited By ~ 10

Author(s):

Sebastian Weber ◽

Walter Traunspurger

Keyword(s):

Species Composition ◽

Cyprinus Carpio ◽

Juvenile Fish ◽

Natural Habitat ◽

Fish Predation ◽

Trophic Levels ◽

Free Living ◽

Food Web Ecology ◽

Freshwater Pond ◽

Predation Effects

Free-living nematodes are well recognised as an abundant and ubiquitous component of meiobenthic communities, where they serve as a link between microbial production and higher trophic levels. However, the effect of fish predation on nematode assemblages is almost unknown. In this study, the predation effects of the benthivorous juvenile carp (Cyprinus carpio) on nematode abundance, biomass, diversity and species composition in the littoral zone of a natural freshwater pond were examined over 310 days using field enclosures and exclosures. Fish predation altered the abundance and biomass of nematodes, and especially of the dominant species Tobrilus gracilis, Eumonhystera filiformis and Monhystera paludicola/stagnalis. Species richness and species composition, but not the diversity and feeding type of nematode assemblages, were affected by fish predation. Our study provides insights into the food-web ecology of lakes and the first evidence of freshwater fish predation effects on nematode assemblages in a natural habitat.

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Regional shifts in phytoplankton succession and primary productivity in the San Antonio Bay System (USA) in response to diminished freshwater inflows

Marine and Freshwater Research ◽

10.1071/mf15223 ◽

2017 ◽

Vol 68 (1) ◽

pp. 131 ◽

Cited By ~ 7

Author(s):

Daniel L. Roelke ◽

Hsiu-Ping Li ◽

Carrie J. Miller-DeBoer ◽

George M. Gable ◽

Stephen E. Davis

Keyword(s):

Primary Productivity ◽

San Antonio ◽

Sampling Period ◽

Phosphorus Limitation ◽

Trophic Levels ◽

Human Consumption ◽

Dry Period ◽

Nitrogen And Phosphorus ◽

Commercially Important ◽

Freshwater Inflows

In many areas of the world, human consumption and climate change threaten freshwater inflows to coastal ecosystems. In the San Antonio Bay System, USA (SABS), freshwater inflows are projected to decrease in the coming decades. Our 30-month sampling period of SABS captured a prolonged period of higher inflows and a prolonged period of lower inflow. Our observations offer insights as to how this system might respond to lower freshwater inflows in the future. Of most importance in our observations was a regional shift that occurred in maximum primary productivity from the middle and lower SABS towards the upper SABS. In addition, a warm-month succession of phytoplankton taxa in the upper SABS that occurred during the wet period did not occur during the dry period. We also observed spatiotemporal shifts in apparent nitrogen- and phosphorus-limitation, with both appearing to influence phytoplankton biomass and primary productivity. Changes to SABS phytoplankton such as these might deleteriously affect organisms of higher trophic levels with life stages that are regionally confined by other factors, such as depth, macrophyte presence, and existence of hard-bottomed substrate, which in this bay system includes both commercially important and endangered species.

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Light alters the impacts of nitrogen and foliar pathogens on the performance of early successional tree seedlings

PeerJ ◽

10.7717/peerj.11587 ◽

2021 ◽

Vol 9 ◽

pp. e11587

Author(s):

Alexander Brown ◽

Robert W. Heckman

Keyword(s):

Fungal Pathogens ◽

Nitrogen Availability ◽

Light Availability ◽

High Light ◽

Plant Performance ◽

Forest Understory ◽

Light Limitation ◽

Tree Seedlings ◽

Low Light ◽

Foliar Damage

Light limitation is a major driver of succession and an important determinant of the performance of shade-intolerant tree seedlings. Shade intolerance may result from a resource allocation strategy characterized by rapid growth and high metabolic costs, which may make shade-intolerant species particularly sensitive to nutrient limitation and pathogen pressure. In this study, we evaluated the degree to which nitrogen availability and fungal pathogen pressure interact to influence plant performance across different light environments. To test this, we manipulated nitrogen availability (high, low) and access by foliar fungal pathogens (sprayed with fungicide, unsprayed) to seedlings of the shade-intolerant tree, Liquidambar styraciflua, growing at low and high light availability, from forest understory to adjacent old field. Foliar fungal damage varied with light and nitrogen availability; in low light, increasing nitrogen availability tripled foliar damage, suggesting that increased nutrient availability in low light makes plants more susceptible to disease. Despite higher foliar damage under low light, spraying fungicide to exclude pathogens promoted 14% greater plant height only under high light conditions. Thus, although nitrogen availability and pathogen pressure each influenced aspects of plant performance, these effects were context dependent and overwhelmed by light limitation. This suggests that failure of shade-intolerant species to invade closed-canopy forest can be explained by light limitation alone.

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Fish and seagrass communities vary across a marine reserve boundary, but seasonal variation in small fish abundance overshadows top-down effects of large consumer exclosures

10.31230/osf.io/kudq5 ◽

2018 ◽

Author(s):

James Douglass ◽

Richard Paperno ◽

Eric A. Reyier ◽

Anson H. Hines

Keyword(s):

Seasonal Variation ◽

Trophic Levels ◽

Fish Abundance ◽

Predatory Fish ◽

Gut Contents ◽

Spatial And Temporal Variation ◽

Small Fish ◽

Ecosystem Structure ◽

Top Down ◽

Exclusion Experiment

A growing number of examples indicate that large predators can alter seagrass ecosystem structure and processes via top-down trophic interactions. However, the nature and strength of those interactions varies with biogeographic context, emphasizing the need for region-specific investigations. We investigated spatial and temporal variation in predatory fish and seagrass communities across a Marine Protected Area (MPA) boundary in the Banana River Lagoon, Florida (USA), assessing trophic roles of intermediate consumers, and performing a large-consumer exclusion experiment in the MPA. Large, predatory fishes were most abundant within the MPA, while some mid-sized fishes were more abundant outside it. Small, seagrass-resident fishes, epifaunal invertebrates, and macrophytes also differed across the MPA boundary, but varied more among individual sites and seasonally. We cannot conclusively attribute these patterns to MPA status because we lack data from prior to MPA establishment and lack study replication at the level of MPA. Nevertheless, other patterns among our data are consistent with hypothesized mechanisms of top-down control. E.g., inverse seasonal patterns in the abundance of organisms at adjacent trophic levels, coupled with stable C and N isotope and gut contents data, suggest top-down control of crustacean grazers by seasonal recruitment of small fishes. Large-consumer exclosures in the MPA increased the abundance of mid-sized predatory and omnivorous fishes, but had few impacts on lower trophic levels. Results suggest that large-scale variation in large, predatory fish abundance in this system does not strongly affect seagrass-resident fish, invertebrate, and algal communities, which appear to be driven more by habitat structure and seasonal variation in small fish abundance.

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The rise of the three-spined stickleback – eco-evolutionary consequences of a mesopredator release

10.1101/2020.05.08.083873 ◽

2020 ◽

Author(s):

Britas Klemens Eriksson ◽

Casey Yanos ◽

Sarah Bourlat ◽

Serena Donadi ◽

Michael C. Fontaine ◽

...

Keyword(s):

Food Web ◽

Food Webs ◽

Stomach Content ◽

Ecological Effects ◽

Trophic Levels ◽

Predatory Fish ◽

Series Data ◽

Food Web Structure ◽

Benthic Production ◽

Invertebrate Herbivores

AbstractDeclines of large predatory fish due to overexploitation are restructuring food webs across the globe. It is now becoming evident that restoring these altered food webs requires addressing not only ecological processes, but evolutionary ones as well, because human-induced rapid evolution may in turn affect ecological dynamics. In the central Baltic Sea, abundances of the mesopredatory fish, the three-spined stickleback (Gasterosteus aculeatus), have increased dramatically during the past decades. Time-series data covering 22 years show that this increase coincides with a decline in the number of juvenile perch (Perca fluviatilis), the most abundant predator of stickleback along the coast. We studied the interaction between evolutionary and ecological effects of this mesopredator take-over, by surveying the armour plate morphology of stickleback and the structure of the associated food web. First, we investigated the distribution of different stickleback phenotypes depending on predator abundances and benthic production; and described the stomach content of the stickleback phenotypes using metabarcoding. Second, we explored differences in the relation between different trophic levels and benthic production, between bays where the relative abundance of fish was dominated by stickleback or not; and compared this to previous cage-experiments to support causality of detected correlations. We found two distinct lateral armour plate phenotypes of stickleback, incompletely and completely plated. The proportion of incompletely plated individuals increased with increasing benthic production and decreasing abundances of adult perch. Stomach content analyses showed that the completely plated individuals had a stronger preference for invertebrate herbivores (amphipods) than the incompletely plated ones. In addition, predator dominance interacted with ecosystem production to determine food web structure and the propagation of a trophic cascade: with increasing production, biomass accumulated on the first (macroalgae) and third (stickleback) trophic levels in stickleback-dominated bays, but on the second trophic level (invertebrate herbivores) in perch-dominated bays. Since armour plates are defence structures favoured by natural selection in the presence of fish predators, the phenotype distribution suggest that a novel low-predation regime favours sticklebacks with less armour. Our results indicate that an interaction between evolutionary and ecological effects of the stickleback take-over has the potential to affect food web dynamics.

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