Oceanographic anomalies coinciding with humpback whale super-group occurrences in the Southern Benguela

AbstractSeasonal feeding behaviour of humpback whales (Megaptera novaeangliae) has been observed in the coastal waters of the Southern Benguela where the species has been observed forming super-groups during the austral spring in recent years since 2011. Super-groups are unprecedented densely-packed aggregations of between 20 and 200 individuals in low-latitude waters and their occurrences indicate possible changes in feeding behaviour of the species. We accessed published data on super-groups occurrence in the study area in 2011, 2014 and 2015, and investigated oceanographic drivers that support prey availability in this region. We found that enhanced primary production is a necessary but not sufficient condition for super-groups to occur. Positive chlorophyll anomalies occurring one month prior to the super-group occurrences were identified, but only a concurrent significantly reduced water volume export from the region throughout October were conducive to the aggregations in the specific years. Hydrodynamic model results attributed the anomalous decreased volume export to the strength and orientation of the Goodhope Jet and associated eddy activity. The combination of random enhanced primary production typical of the region and emerging anomalous conditions of reduced water export in October since 2011 resulted in favourable food availability leading to the unique humpback whale aggregations. The novelty of this grouping behaviour is indicative of the lack of such oceanographic conditions in the past. Given the recency of the events, it is difficult to attribute this reduction in ocean transport to climatic regime shifts, and the origin should be likely investigated in the distant water mass interaction with the greater Agulhas system rather than in local intensifications of the upwelling conditions. A positive trend in the humpback whale population abundance points to the need to monitor the exposure of the species to the changing climate conditions.

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The spatial heterogeneity of the relationship between gross primary production and sun-induced chlorophyll fluorescence regulated by climate conditions during 2007-2018

Global Ecology and Conservation ◽

10.1016/j.gecco.2021.e01721 ◽

2021 ◽

pp. e01721

Author(s):

Yonglin Wang ◽

Lei Zhou ◽

Jie Zhuang ◽

Leigang Sun ◽

Yonggang Chi

Keyword(s):

Chlorophyll Fluorescence ◽

Primary Production ◽

Spatial Heterogeneity ◽

Gross Primary Production ◽

Climate Conditions ◽

The Relationship

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Interaction between prey availability and feeding behaviour of age-1 and age-2 perch (Perca fluviatilis L.) in a biomanipulated lake (Bautzen Reservoir, Germany)

Limnologica ◽

10.1016/s0075-9511(01)80042-6 ◽

2001 ◽

Vol 31 (1) ◽

pp. 11-16 ◽

Cited By ~ 9

Author(s):

Hendrik Dörner ◽

Heinz Schultz ◽

Thomas Mehner ◽

Jürgen Benndorf

Keyword(s):

Feeding Behaviour ◽

Prey Availability ◽

Perca Fluviatilis ◽

Perch Perca Fluviatilis

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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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Ecology of gyrfalcons, Falco rusticolus, in the central Canadian Arctic: diet and feeding behaviour

Canadian Journal of Zoology ◽

10.1139/z88-050 ◽

1988 ◽

Vol 66 (2) ◽

pp. 334-344 ◽

Cited By ~ 23

Author(s):

K. G. Poole ◽

D. A. Boag

Keyword(s):

Feeding Behaviour ◽

Prey Species ◽

Prey Availability ◽

Optimal Foraging Theory ◽

Ground Squirrels ◽

Spermophilus Parryii ◽

Falco Rusticolus ◽

Lagopus Mutus ◽

Spring Arrival ◽

Average Size

Diet and aspects of feeding behaviour in a population of gyrfalcons (Falco rusticolus) in the Northwest Territories were examined between 1984 and 1986. Three prey species, rock ptarmigan (Lagopus mutus), arctic ground squirrel (Spermophilus parryii), and arctic hare (Lepus arcticus), composed 96.5% of total prey biomass identified. Ptarmigan and hares were taken in May and June of all years (98.2% of biomass). Juvenile squirrels were used extensively in July and August of 1984 and 1985 but not in 1986, when squirrel production fell to almost zero; ptarmigan continued to be the dominant prey species throughout that summer. Because densities of breeding ptarmigan remained relatively constant during the study, but those of juvenile ground squirrels did not, it appeared that gyrfalcons responded functionally to varying availability of prey. Mean weight (250 g) of prey taken by male gyrfalcons was significantly less than the weight (330 g) of prey taken by females. As predicted by optimal foraging theory, average size of prey brought to the nest increased as time away from the nest increased. Conditions of food abundance were observed at most nests, suggesting that the amount of food available during the nestling period was not limiting production. We suggest that annual production is a function of spacing of pairs, which is set during courtship and prelaying, when prey availability is at its yearly low and when males must forage for both members of the pair. The fact that most gyrfalcon pairs initiated laying only after the spring arrival of migrating ptarmigan is consistent with this conclusion.

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Measurements of Phytoplankton Absorption Other Than Per Unit of Chlorophyll a

Ocean Optics ◽

10.1093/oso/9780195068436.003.0010 ◽

1994 ◽

Author(s):

Mary Jane Perry

Keyword(s):

Primary Production ◽

Chlorophyll A ◽

Photosynthetic Pigments ◽

Critical Role ◽

Specific Effect ◽

Water Volume ◽

Phytoplankton Abundance ◽

Chlorophyll A Concentration ◽

Total Irradiance ◽

Phytoplankton Absorption

Phytoplankton plays a critical role in determining light fields of the world’s oceans, primarily through absorption of light by photosynthetic pigments (see Chapters 1 to 5). Consequently there has been considerable interest from optical researchers in determining phytoplankton absorption. Conversely, from the biological point of view, this absorption assumes paramount importance because it is the sole source of energy for photosynthesis and thus should be central to direct estimates of primary production. There are two logical parts in determining this effect of phytoplankton and in estimating primary production. One is the estimation of abundance, and the other is estimation of specific effect or specific production rate. The earliest estimates of phytoplankton abundance were based on cell counts. From the time of Francis A. Richards’ Ph.D. dissertation, however, measurement of chlorophyll a concentration per unit of water volume, because of its relative ease, has assumed a central role in abundance estimation. Physiological studies and technological advances in optical instrumentation over the last decade lead me to question whether the continued use of chlorophyll a concentration to estimate phytoplankton abundance was wise either from the viewpoint of narrowing confidence intervals on estimates of absorption and production or from the viewpoint of mechanistic understanding of the processes involved. The measurement of chlorophyll a has become such a routine tool of biological oceanography, however, that the reasons for my heresy require elaboration. Some of the reasons are not too subtle. Chlorophyll a exists with other photosynthetic pigments in organized arrays associated with photosynthetic membranes. The function of these arrays is to harvest photons and transfer their energy to the specialized reaction center complexes that mediate photochemistry (see Chapter 9). The size of the arrays or packages and the ratio of chlorophyll a molecules to other light-harvesting pigments within the packages vary with phytoplankton cell size, total irradiance and its spectral distribution, as well as with other environmental parameters. It is well known that dark-adapted (= light-limited) cells increase their complements of photopigments. This plasticity in pigment packaging is evidenced in the variability of chlorophyll a-specific absorption coefficients. Simple optical models based only on chlorophyll a concentrations cannot be accurate or precise unless the effects of pigment packaging are considered.

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Quantum yield of the marine benthic microflora of near-shore coastal Penang, Malaysia

Marine and Freshwater Research ◽

10.1071/mf05007 ◽

2005 ◽

Vol 56 (7) ◽

pp. 1047 ◽

Cited By ~ 3

Author(s):

A. McMinn ◽

S. Sellah ◽

W. A. Wan Ab. Llah ◽

M. Mohammad ◽

F. Md. Sidik Merican ◽

...

Keyword(s):

Primary Production ◽

Suspended Solids ◽

Euphotic Zone ◽

Water Clarity ◽

Quantum Yields ◽

Chl A ◽

Near Shore ◽

High Concentrations ◽

A Minor ◽

Reduced Water

Benthic microalgal communities often contribute more than 30% of the primary production of shallow coastal and estuarine areas. At Muka Head Penang (Pulau Pinang) and the Songsong Islands (Pulau Songsong), Kedah, Malaysia, high concentrations of suspended solids and phytoplankton biomass (10.6 mg Chl a m−3) has reduced water clarity such that the euphotic zone of these areas is less than 2 m and 3 m deep respectively. The benthic microalgal communities, which were composed of the diatom genera Cocconeis, Fragilaria, Paralia and Pleurosigma, had a low biomass, had low maximum quantum yields (0.325 ± 0.129), were poorly adapted to their light environment and were constantly light limited. These characteristics suggest that the benthic microalgal communities were likely to have made only a minor contribution to the total primary production of the area.

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Water Intake, Water Balance, and the Elusive Daily Water Requirement

Nutrients ◽

10.3390/nu10121928 ◽

2018 ◽

Vol 10 (12) ◽

pp. 1928 ◽

Cited By ~ 36

Author(s):

Lawrence Armstrong ◽

Evan Johnson

Keyword(s):

Water Balance ◽

Life Stage ◽

Body Water ◽

Water Volume ◽

Published Data ◽

Water Requirements ◽

Neuroendocrine Response ◽

Organ Systems ◽

Daily Water ◽

The Brain

Water is essential for metabolism, substrate transport across membranes, cellular homeostasis, temperature regulation, and circulatory function. Although nutritional and physiological research teams and professional organizations have described the daily total water intakes (TWI, L/24h) and Adequate Intakes (AI) of children, women, and men, there is no widespread consensus regarding the human water requirements of different demographic groups. These requirements remain undefined because of the dynamic complexity inherent in the human water regulatory network, which involves the central nervous system and several organ systems, as well as large inter-individual differences. The present review analyzes published evidence that is relevant to these issues and presents a novel approach to assessing the daily water requirements of individuals in all sex and life-stage groups, as an alternative to AI values based on survey data. This empirical method focuses on the intensity of a specific neuroendocrine response (e.g., plasma arginine vasopressin (AVP) concentration) employed by the brain to regulate total body water volume and concentration. We consider this autonomically-controlled neuroendocrine response to be an inherent hydration biomarker and one means by which the brain maintains good health and optimal function. We also propose that this individualized method defines the elusive state of euhydration (i.e., water balance) and distinguishes it from hypohydration. Using plasma AVP concentration to analyze multiple published data sets that included both men and women, we determined that a mild neuroendocrine defense of body water commences when TWI is ˂1.8 L/24h, that 19–71% of adults in various countries consume less than this TWI each day, and consuming less than the 24-h water AI may influence the risk of dysfunctional metabolism and chronic diseases.

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Evolvability meets biogeography: evolutionary potential decreases at high and low environmental favourability

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2017.0516 ◽

2017 ◽

Vol 284 (1856) ◽

pp. 20170516 ◽

Cited By ~ 4

Author(s):

J. Martínez-Padilla ◽

A. Estrada ◽

R. Early ◽

F. Garcia-Gonzalez

Keyword(s):

Environmental Change ◽

Morphological Traits ◽

Evolutionary Dynamics ◽

Environmental Variation ◽

Phenotypic Traits ◽

Published Data ◽

Evolutionary Potential ◽

Critical Question ◽

Climate Conditions ◽

Environmental Selection

Understanding and forecasting the effects of environmental change on wild populations requires knowledge on a critical question: do populations have the ability to evolve in response to that change? However, our knowledge on how evolution works in wild conditions under different environmental circumstances is extremely limited. We investigated how environmental variation influences the evolutionary potential of phenotypic traits. We used published data to collect or calculate 135 estimates of evolvability of morphological traits of European wild bird populations. We characterized the environmental favourability of each population throughout the species' breeding distribution. Our results suggest that the evolutionary potential of morphological traits decreases as environmental favourability becomes high or low. Strong environmental selection pressures and high intra-specific competition may reduce species' evolutionary potential in low- and high- favourability areas, respectively. This suggests that species may be least able to adapt to new climate conditions at their range margins and at the centre. Our results underscore the need to consider the evolutionary potential of populations when studying the drivers of species distributions, particularly when predicting the effects of environmental change. We discuss the utility of integrating evolutionary dynamics into a biogeographical perspective to understand how environmental variation shapes evolutionary patterns. This approach would also produce more reliable predictions about the effect of environmental change on population persistence and therefore on biodiversity.

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Improper management of dams constructed with local materials, infiltration risk and wasted electric energy

MATEC Web of Conferences ◽

10.1051/matecconf/201817809009 ◽

2018 ◽

Vol 178 ◽

pp. 09009

Author(s):

Victorita Radulescu

Keyword(s):

Cross Sections ◽

Electric Energy ◽

Water Volume ◽

Hydropower Plants ◽

Flow Through ◽

Different Dimensions ◽

Study Case ◽

The Mathematical Model ◽

Local Materials ◽

Reduced Water

The present paper presents a study case of improper dike rehabilitation and inefficient management of the water volume from two hydropower lakes, with dams built with local materials. In Romania, with its high hydrographic potential, this solution was adopted for construction of more than 600 hydropower plants, many of them now confronted with infiltration and erosion, and appeared into lateral sides of the dikes. The paper covers some theoretical and practical aspects referring to the functioning of hydropower lakes, establishing the cross-sections with problems in exploitation. Reduced water level produces less electric energy than initially estimated. The dam's construction was not correlated with the geomorphologic conditions and climatic parameters, being necessary supplementary measurements and data acquisition to calibrate the numerical model. There are mentioned some considerations referring at the mathematical model, based on new hypotheses of infiltration through sediments with different dimensions and characteristics. The flow through dikes is assumed non-permanent due to massive infiltration. Part of the numerical modeling, the obtained velocities of infiltration, and the streamlines are illustrated. The results of the tested solution prove its efficiency and allow illustrating and some other sections with possible risk in functioning. Some discussions, conclusions, and references are finally presented.

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