scholarly journals Trophic control of cryptic coralline algal diversity

2019 ◽  
Vol 116 (30) ◽  
pp. 15080-15085 ◽  
Author(s):  
Katharine R. Hind ◽  
Samuel Starko ◽  
Jenn M. Burt ◽  
Matthew A. Lemay ◽  
Anne K. Salomon ◽  
...  
Keyword(s):  
Algal Species ◽  
Trophic Dynamics ◽  
Kelp Forests ◽  
Negative Consequences ◽  
Food Web Structure ◽  
Nearshore Ecosystems ◽  
Keystone Predation ◽  
Ecological Patterns ◽  
Ecosystem Level ◽  
Algal Assemblages

Understanding how trophic dynamics drive variation in biodiversity is essential for predicting the outcomes of trophic downgrading across the world’s ecosystems. However, assessing the biodiversity of morphologically cryptic lineages can be problematic, yet may be crucial to understanding ecological patterns. Shifts in keystone predation that favor increases in herbivore abundance tend to have negative consequences for the biodiversity of primary producers. However, in nearshore ecosystems, coralline algal cover increases when herbivory is intense, suggesting that corallines may uniquely benefit from trophic downgrading. Because many coralline algal species are morphologically cryptic and their diversity has been globally underestimated, increasing the resolution at which we distinguish species could dramatically alter our conclusions about the consequences of trophic dynamics for this group. In this study, we used DNA barcoding to compare the diversity and composition of cryptic coralline algal assemblages at sites that differ in urchin biomass and keystone predation by sea otters. We show that while coralline cover is greater in urchin-dominated sites (or “barrens”), which are subject to intense grazing, coralline assemblages in these urchin barrens are significantly less diverse than in kelp forests and are dominated by only 1 or 2 species. These findings clarify how food web structure relates to coralline community composition and reconcile patterns of total coralline cover with the widely documented pattern that keystone predation promotes biodiversity. Shifts in coralline diversity and distribution associated with transitions from kelp forests to urchin barrens could have ecosystem-level effects that would be missed by ignoring cryptic species’ identities.

scholarly journals Algal community composition within territories of the damselfish Stegastes nigricans (Pomacentridae, Labroidei) in Fiji and the Cook Islands

2005 ◽  
Vol 23 (1) ◽  
pp. 43 ◽  
Author(s):  
L W Zemke-White ◽  
E L Beatson
Keyword(s):  
Species Composition ◽  
Community Composition ◽  
Algal Species ◽  
Abundant Species ◽  
Red Alga ◽  
Algal Community ◽  
Filamentous Algae ◽  
Cook Islands ◽  
Algal Assemblages

The species composition of algal assemblages inside territories of the damselfish Stegastes nigricans was examined from Nananu-i-ra Island, Fiji and Rarotonga, Cook Islands. A total of 32 algal species were identified, the majority of them Rhodophytes (24 species). Seven species were unique to Rarotonga, six were unique to Fiji, with the remaining 19 species recorded at both locations. The biodiversity of territories was similar at both locations. The red alga, Herposiphonia secunda, was the most abundant species found, comprising 40.33% � 3.51SE and 33.94% � 3.58SE from Rarotonga and Fiji respectively. Gelidiopsis intricata, Polysiphonia sp., Aglaothamnion cordatum, and various Cyanophytes were also abundant at both locations. As a group, filamentous algae accounted for 70.35% of the algae found within the territories at all sites. We suggest that if S. nigricans are actively weeding their territories, they are selecting filamentous algae, and particularly Herposiphonia sp. and Polysiphonia sp.

Is pelagic top-down control in lakes augmented by benthic energy pathways?

2005 ◽  
Vol 62 (6) ◽  
pp. 1422-1431 ◽  
Author(s):  
M Jake Vander Zanden ◽  
Timothy E Essington ◽  
Yvonne Vadeboncoeur
Keyword(s):  
Food Web ◽  
Energy Flow ◽  
Standing Stock ◽  
Fold Increase ◽  
Trophic Dynamics ◽  
Prey Fish ◽  
Top Down ◽  
Food Web Structure ◽  
Contrast Analysis ◽  
Dynamic Perspective

Modern food web studies are typically conducted from a trophic dynamic perspective that focuses on combined roles of top-down and bottom-up forces in regulating food web structure. Recognition of spatial food web subsidies in diverse ecosystems highlights the importance of energy flow as a foundation for understanding trophic dynamics. Here, we consider how different energy flow configurations might affect trophic dynamics in north-temperate lakes. A literature review revealed that littoral piscivores exert top-down control on prey fishes. In contrast, analysis of littoral predator diets indicated extensive omnivory and heavy reliance on zoobenthic prey. We explored this uncoupling between trophic dynamics (piscivores regulate prey fish) and energy flow (zoobenthos in piscivore diets) using a biomass dynamic model. This model compared top-down impacts of a piscivore on prey fishes under two scenarios: consumption of prey fish only and consumption of prey fish plus zoobenthos. The model predicted that elimination of zoobenthivory leads to a 50% reduction in piscivore standing stock and concomitant 2.5-fold increase in prey fish abundance (i.e., zoobenthivory plays a key role in mediating pelagic top-down control). These results highlight the role of benthic–pelagic linkages in regulating trophic dynamics and underscore the value of whole-ecosystem approaches to the study of food webs.

Periphyton communities in New Zealand streams impacted by acid mine drainage

2008 ◽  
Vol 59 (12) ◽  
pp. 1084 ◽  
Author(s):  
Jonathan P. Bray ◽  
Paul A. Broady ◽  
Dev K. Niyogi ◽  
Jon S. Harding
Keyword(s):  
New Zealand ◽  
Acid Mine Drainage ◽  
Metal Oxides ◽  
Mine Drainage ◽  
Algal Species ◽  
Taxonomic Richness ◽  
Algal Communities ◽  
Acid Mine ◽  
Algal Assemblages ◽  
Abiotic And Biotic Factors

Discharges from historic and current coal mines frequently generate waters low in pH (<3), high in heavy metals (e.g. Fe, Al) and cover streambeds in metal precipitates. The present study investigated periphyton communities at 52 stream sites on the West Coast, South Island, New Zealand, representing a range of impacts from acid mine drainage (AMD). Taxonomic richness was negatively related to acidity and metal oxides and biomass was negatively correlated with metal oxides, but positively related to acidity. Streams with low pH (<3.5) had low periphyton richness (14 taxa across all sites) and were dominated by Klebsormidium acidophilum, Navicula cincta and Euglena mutabilis. As pH increased, so did taxonomic richness while community dominance decreased and community composition became more variable. Canonical correspondence analyses of algal assemblages revealed patterns influenced by pH. These findings indicate that streams affected by AMD possess a predictable assemblage composition of algal species that can tolerate the extreme water chemistry and substrate conditions. The predictability of algal communities declines with decreasing stress, as other abiotic and biotic factors become increasingly more important.

scholarly journals Production of mobile invertebrate communities on shallow reefs from temperate to tropical seas

2020 ◽  
Vol 287 (1941) ◽  
pp. 20201798
Author(s):  
K. M. Fraser ◽  
J. S. Lefcheck ◽  
S. D. Ling ◽  
C. Mellin ◽  
R. D. Stuart-Smith ◽  
...  
Keyword(s):  
Primary Productivity ◽  
Human Impacts ◽  
Anthropogenic Impacts ◽  
Selection Procedure ◽  
Marine Ecosystems ◽  
Environmental Drivers ◽  
Kelp Forests ◽  
Food Web Structure ◽  
Continental Scale ◽  
Biogenic Habitat

Primary productivity of marine ecosystems is largely driven by broad gradients in environmental and ecological properties. By contrast, secondary productivity tends to be more variable, influenced by bottom-up (resource-driven) and top-down (predatory) processes, other environmental drivers, and mediation by the physical structure of habitats. Here, we use a continental-scale dataset on small mobile invertebrates (epifauna), common on surfaces in all marine ecosystems, to test influences of potential drivers of temperature-standardized secondary production across a large biogeographic range. We found epifaunal production to be remarkably consistent along a temperate to tropical Australian latitudinal gradient of 28.6°, spanning kelp forests to coral reefs (approx. 3500 km). Using a model selection procedure, epifaunal production was primarily related to biogenic habitat group, which explained up to 45% of total variability. Production was otherwise invariant to predictors capturing primary productivity, the local biomass of fishes (proxy for predation pressure), and environmental, geographical, and human impacts. Highly predictable levels of epifaunal productivity associated with distinct habitat groups across continental scales should allow accurate modelling of the contributions of these ubiquitous invertebrates to coastal food webs, thus improving understanding of likely changes to food web structure with ocean warming and other anthropogenic impacts on marine ecosystems.

scholarly journals Algal assemblages in springs of different lithologies (ophiolites vs. limestone) of the Konjuh Mountain (Bosnia And Herzegovina)

2019 ◽  
Vol 78 (1) ◽  
pp. 66-81 ◽  
Author(s):  
Jasmina Kamberović ◽  
Anđelka Plenković-Moraj ◽  
Koraljka Kralj Borojević ◽  
Marija Gligora Udovič ◽  
Petar Žutinić ◽  
...  
Keyword(s):  
Diversity Index ◽  
Anthropogenic Impacts ◽  
Algal Species ◽  
Algal Communities ◽  
Morphological Alterations ◽  
Wiener Diversity Index ◽  
Algal Abundance ◽  
Algal Assemblages ◽  
Spring Type ◽  
Cyanobacterial Genus

Abstract The biodiversity of algal communities and environmental conditions were investigated in the springs of Mt. Konjuh. The assemblages of 20 springs emerging from different lithologies (limestones and ophiolites, respectively) comprised 234 algal taxa. Diatoms and cyanobacteria were the most species-rich groups. The most common alkaliphilic, circumneutral, and eutraphentic diatoms were represented by the genera Gomphonema, Nitzschia, Navicula, Cymbella, and Achnanthidium, and by the cyanobacterial genus Phormidium. Hierarchical clustering and SIMPROF analysis based on relative algal abundance clustered springs into six groups, separating them mainly according to spring type and lithology. Indicator species for groups and springs on different lithological substrata were singled out, revealing 33 taxa with preferences for ophiolites, and 20 taxa with preferences for carbonates. The values of the Shannon-Wiener diversity index were moderately high per spring location, and similar for the two groups of springs on different lithologies. A higher similarity in species composition was noted between springs on ophiolites and limestones than between springs on ophiolites and other types of siliceous substrata. The present study suggests that algal assemblages in springs emerging from ophiolites, even those made up by a preponderance of silicates, should be analyzed separately from those related to springs on other siliceous substrata. The results obtained showed that most of the springs studied are affected by anthropogenic impacts and morphological alterations leading to the dominance of highly competitive meso- and eutraphentic algal species, thus emphasizing the importance of further investigation and conservation of these habitats.

Direct and Indirect Effects of Consumers on Benthic Algae in Isolated Pools of an Ephemeral Stream

1990 ◽  
Vol 47 (10) ◽  
pp. 2057-2065 ◽  
Author(s):  
Paul V. McCormick
Keyword(s):  
Algal Biomass ◽  
Algal Species ◽  
Algal Growth ◽  
Benthic Algae ◽  
Nitrogen Enrichment ◽  
Direct And Indirect Effects ◽  
Ephemeral Stream ◽  
Positive Effects ◽  
Algal Assemblages ◽  
Trophic Connections

Artificial pools were used to test for interactions among dominant consumer and producer populations that coexist in isolated pools of an ephemeral stream each summer. Nitrogen and/or phosphorus were supplied to one set of pools; herbivorous snails and crayfish and a predaceous centrarchid were added in different combinations to other pools. Algal growth was measured inside and outside wire cages placed in pools to exclude herbivores and/or predators. Algal biomass and the abundance of most algal species were increased by nitrogen enrichment. Algal biomass was also enhanced by addition of consumers. There were few differences in structure between algal assemblages inside and outside cages in any treatment. Under conditions of nitrogen limitation, moderate levels of herbivory can enhance algal growth. Positive effects are greatest at the microsite level and may depend on the ability of algal species to resist digestion by grazers. Predators may affect the algal assemblage indirectly by reducing herbivore survival or activity and directly by converting nutrients stored in herbivore biomass into a form available for algal growth. Because the importance of different trophic connections may vary among ecosystems, experimentation must consider all those that are potentially important.

scholarly journals Long-term changes in the algal composition of the Vaal River, South Africa – did the Lesotho Highlands Water Project play a role?

2013 ◽  
Vol 32 (1) ◽  
Author(s):  
Sanet Janse van Vuuren ◽  
Annelie Swanepoel ◽  
Germarie Van Zyl
Keyword(s):  
Algal Blooms ◽  
Algal Species ◽  
River System ◽  
Algal Concentration ◽  
Water Demands ◽  
Vaal River ◽  
Algal Assemblages ◽  
Lesotho Highlands Water Project ◽  
Algal Composition

The Vaal River has become so nutrient-enriched that algal blooms pose problems. A unique opportunity arose to determine if there were changes in the chemistry en algal composition of the Vaal River after oligomesotrophic Katse Dam (Lesotho) water was imported to augment supplies in the light of growing water demands in the Vaal River catchment area. Algal concentration and composition in the Vaal River during three periods (between 1992 and 1994, 1998 and 2000, as well as 2004 and 2006) were compared to those in the Katse Dam (1998–2006). Some algal species, initially absent from the Vaal River, appeared in the river during and after transfer. Mixed algal assemblages found in the Vaal River before transfer of Katse Dam water gradually changed after transfer to assemblages mainly composed of cyanobacteria. The total algal concentration in the Vaal River Barrage doubled from the period between 1992 and 1994 to that between 2004 and 2006, indicating that the transfer of clear, oligomesotrophic Katse Dam water did not dilute the eutrophic Vaal River water sufficiently in order to reduce algal concentrations. Results showed that continuous downstream pollution and eutrophication of the Vaal River system eliminated the diluting effect of Katse imports. This resulted in changes in algal composition and concentration in the Vaal, characteristic of those associated with increasing eutrophication.

Combining scientific and fishers’ knowledge to co-create indicators of food web structure and function

2019 ◽  
Author(s):  
Jacob W Bentley ◽  
David E Hines ◽  
Stuart R Borrett ◽  
Natalia Serpetti ◽  
Gema Hernandez-Milian ◽  
...  
Keyword(s):  
Food Web ◽  
Integrated Management ◽  
Irish Sea ◽  
Food Web Structure ◽  
Predator Prey ◽  
Before And After ◽  
Commercial Species ◽  
Ecosystem Level ◽  
The Irish Sea ◽  
And Function

Abstract In this study, we describe the approach taken by the International Council for the Exploration of the Seas Irish Sea benchmark working group (WKIrish), to co-create diet information for six commercial species using fishers' and scientists knowledge and incorporate it into an existing Ecopath food web model of the Irish Sea. To understand how the co-created diet information changed the model we compared a suite of food web indicators before and after the addition of fishers' knowledge (FK). Of the 80 predator–prey interactions suggested by fishers during workshops, 50 were already included in the model. Although the small number of changes made to the model structure had an insignificant impact on the ecosystem-level indicators, indicators of species hierarchical importance and mixed trophic impacts were significantly changed, particularly for commercial species. FK heightened the importance of discards as a source of food for rays, plaice, and whiting and reduced the importance of cod, toothed whales, and plaice as structural components of the food web. FK therefore led to changes which will influence pairwise advice derived from the model. We conclude by providing lessons from WKIrish which we believe were key to the positive co-production experience and development of integrated management.

Determining Emotional Tone and Verbal Behavior in Patients With Tinnitus and Hyperacusis: An Exploratory Mixed-Methods Study

2019 ◽  
Vol 28 (3) ◽  
pp. 660-672
Author(s):  
Suzanne H. Kimball ◽  
Toby Hamilton ◽  
Erin Benear ◽  
Jonathan Baldwin
Keyword(s):  
Mixed Methods ◽  
Verbal Behavior ◽  
Coping Strategies ◽  
Mixed Methods Study ◽  
Self Report ◽  
Anxiety And Depression ◽  
Negative Consequences ◽  
Emotional Tone ◽  
Explanatory Mixed Methods ◽  
Quantitative Results

Purpose The purpose of this study was to evaluate the emotional tone and verbal behavior of social media users who self-identified as having tinnitus and/or hyperacusis that caused self-described negative consequences on daily life or health. Research Design and Method An explanatory mixed-methods design was utilized. Two hundred “initial” and 200 “reply” Facebook posts were collected from members of a tinnitus group and a hyperacusis group. Data were analyzed via the LIWC 2015 software program and compared to typical bloggers. As this was an explanatory mixed-methods study, we used qualitative thematic analyses to explain, interpret, and illustrate the quantitative results. Results Overall, quantitative results indicated lower overall emotional tone for all categories (tinnitus and hyperacusis, initial and reply), which was mostly influenced by higher negative emotion. Higher levels of authenticity or truth were found in the hyperacusis sample but not in the tinnitus sample. Lower levels of clout (social standing) were indicated in all groups, and a lower level of analytical thinking style (concepts and complex categories rather than narratives) was found in the hyperacusis sample. Additional analysis of the language indicated higher levels of sadness and anxiety in all groups and lower levels of anger, particularly for initial replies. These data support prior findings indicating higher levels of anxiety and depression in this patient population based on the actual words in blog posts and not from self-report questionnaires. Qualitative results identified 3 major themes from both the tinnitus and hyperacusis texts: suffering, negative emotional tone, and coping strategies. Conclusions Results from this study suggest support for the predominant clinical view that patients with tinnitus and hyperacusis have higher levels of anxiety and depression than the general population. The extent of the suffering described and patterns of coping strategies suggest clinical practice patterns and the need for research in implementing improved practice plans.

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