scholarly journals Marine Heatwaves Exceed Cardiac Thermal Limits of Adult Sparid Fish (Diplodus capensis, Smith 1884)

2021 ◽  
Vol 8 ◽  
Author(s):  
Kerry-Ann van der Walt ◽  
Warren M. Potts ◽  
Francesca Porri ◽  
Alexander C. Winkler ◽  
Murray I. Duncan ◽  
...  
Keyword(s):  
Heart Rate ◽  
East Coast ◽  
Reaction Rates ◽  
Range Limit ◽  
Thermal Indices ◽  
Thermal Thresholds ◽  
Thermal Limits ◽  
Relative Change ◽  
Warm Temperate ◽  
Established Technique

Climate change not only drives increases in global mean ocean temperatures, but also in the intensity and duration of marine heatwaves (MHWs), with potentially deleterious effects on local fishes. A first step to assess the vulnerability of fishes to MHWs is to quantify their upper thermal thresholds and contrast these limits against current and future ocean temperatures during such heating events. Heart failure is considered a primary mechanism governing the upper thermal limits of fishes and begins to occur at temperatures where heart rate fails to keep pace with thermal dependency of reaction rates. This point is identified by estimating the Arrhenius breakpoint temperature (TAB), which is the temperature where maximum heart rate (fHmax) first deviates from its exponential increase with temperature and the incremental Q10 breakpoint temperature (TQB), which is where the Q10 temperature coefficient (relative change in heart rate for a 10°C increase in temperature) for fHmax abruptly decreases during acute warming. Here we determined TAB, TQB and the temperature that causes cardiac arrhythmia (TARR) in adults of the marine sparid, Diplodus capensis, using an established technique. Using these thermal indices results, we further estimated adult D. capensis vulnerability to contemporary MHWs and increases in ocean temperatures along the warm-temperate south-east coast of South Africa. For the established technique, we stimulated fHmax with atropine and isoproterenol and used internal heart rate loggers to measure fHmax under conditions of acute warming in the laboratory. We estimated average TAB, TQB, and TARR values of 20.8°C, 21.0°C, and 28.3°C. These findings indicate that the physiology of D. capensis will be progressively compromised when temperatures exceed 21.0°C up to a thermal end-point of 28.3°C. Recent MHWs along the warm-temperate south-east coast, furthermore, are already occurring within the TARR threshold (26.6–30.0°C) for cardiac function in adult D. capensis, suggesting that this species may already be physiologically compromised by MHWs. Predicted increases in mean ocean temperatures of a conservative 2.0°C, may further result in adult D. capensis experiencing more frequent MHWs as well as a contraction of the northern range limit of this species as mean summer temperatures exceed the average TARR of 28.3°C.

Cyclacanthia n.g. (Demospongiae: Poecilosclerida: Latrunculiidae incertea sedis), a new genus of marine sponges from South African waters, and description of two new species

Zootaxa ◽  
2004 ◽  
Vol 725 (1) ◽  
pp. 1 ◽  
Author(s):  
TOUFIEK SAMAAI ◽  
VASHA GOVENDER ◽  
MICHELLE KELLY
Keyword(s):  
South African ◽  
Type Species ◽  
New Genus ◽  
East Coast ◽  
Hot Spot ◽  
Marine Sponges ◽  
The Family ◽  
Two New Species ◽  
Shallow Subtidal ◽  
Warm Temperate

The new genus Cyclacanthia n.g. is erected in the poecilosclerid Family Latrunculiidae for the type species Latrunculia bellae Samaai & Kelly, 2003, and two further species, Cyclacanthia cloverlyae sp. nov., and Cyclacanthia mzimayiensis sp. nov.. The latter species are from the subtropical east coast of South Africa, whereas C. bellae has only been found further south in warm temperate Algoa Bay. Cyclacanthia n.g. differs from other Latrunculiidae genera in the ontogeny, morphology and structure of the mature microsclere, the isospinodiscorhabd, which has only three major whorls of projections as opposed to the four in species of Latrunculia du Bocage. Additional diagnostic characters include the presence of broad swathes of megascleres that diverge from the base of the sponge towards the upper choanosome, where they form loose brushes and the typical whispy reticulation of most Latrunculiidae. The ectosome is composed of a dense tangential layer of megascleres, an irregular palisade of microscleres at the surface, and a permanently encrusting habit. Cyclacanthia n.g. is the second new latrunculid genus recently described from shallow subtidal South African waters, following major revision of the family. The presence of species in four of the five known genera in the family, on South African coastlines, suggests a diversity hot-spot for the family in this region.

Initial ventilatory and circulatory responses to dynamic exercise are slowed in the elderly

2000 ◽  
Vol 89 (5) ◽  
pp. 1771-1777 ◽  
Author(s):  
Koji Ishida ◽  
Yasutake Sato ◽  
Keisho Katayama ◽  
Miharu Miyamura
Keyword(s):  
Heart Rate ◽  
Minute Ventilation ◽  
The Elderly ◽  
Voluntary Exercise ◽  
Elderly Men ◽  
Circulatory Response ◽  
Leg Extension ◽  
Healthy Elderly ◽  
Relative Change ◽  
Passive Movements

To elucidate the characteristics of ventilatory and circulatory responses at the onset of brief and light exercise in the elderly, 13 healthy, elderly men, aged 66.8 yr (mean), exerted bilateral leg extension-flexion movements for only 20 s with a weight around each ankle, with each weight being ∼2.5% of their body mass. Similar movements were passively performed on the subjects by the experimenters. These results were compared with those of 13 healthy, young men (22.9 yr). Minute ventilation increased at the onset of voluntary exercise and passive movements in both groups but showed a slower increase in the elderly. Heart rate also increased in both groups but showed less change in the elderly. Mean blood pressure temporarily decreased in both groups but less in the elderly. The magnitude of relative change (gain) of heart rate in the elderly was significantly smaller than that in the young, whereas the increasing rate to reach one-half of the gain (response time) of ventilation in the elderly was significantly slower than that in the young. Similar tendencies were observed in the passive movements. It is concluded that the elderly show slower ventilatory response and attenuated circulatory response at the onset of dynamic voluntary exercise and passive movements.

Taxonomic Review of the perciform fish genus Acanthistius from the east coast of southern Africa, with description of a new species and designation of a neotype for Serranus sebastoides Castelnau, 1861

Zootaxa ◽  
2010 ◽  
Vol 2352 (1) ◽  
pp. 59 ◽  
Author(s):  
PHILLIP C. HEEMSTRA
Keyword(s):  
South Africa ◽  
New Species ◽  
South America ◽  
Southern Africa ◽  
East Coast ◽  
Valid Species ◽  
Shallow Waters ◽  
Single Specimen ◽  
Warm Temperate ◽  
A New Species

The genus Acanthistius Gill, 1862 comprises ten putative valid species occurring in shallow warm-temperate waters of the Southern Hemisphere: South America (coasts of Ecuador, Peru, Chile, Brazil, and Argentina) southern Africa (Namibia and South Africa), southern Australia, New Zealand, Lord Howe, Norfolk, Kermadec and Easter, and Sala y Gómez islands. Two species: Acanthistius sebastoides (Castelnau, 1861) and Acanthistius sp are known from shallow waters of the east coast of South Africa (Heemstra and Randall, 1986). The latter taxon, previously known from a brief description of a single specimen, is here described from 23 specimens and named Acanthistius joanae. Acanthistius sebastoides is redescribed from 13 specimens and compared with A. joanae and species of Acanthistius known from South America and Australia. A neotype is designated for Serranus sebastoides Castelnau, 1861, as the two syntypes are apparently lost.

Marine mammals and Japanese long-line fishing vessels in Australian waters: operational interactions and sightings

2006 ◽  
Vol 12 (1) ◽  
pp. 31 ◽  
Author(s):  
Catherine Bell ◽  
Peter Shaughnessy ◽  
Margie Morrice ◽  
Bob Stanley
Keyword(s):  
Marine Mammal ◽  
Marine Mammals ◽  
East Coast ◽  
Fishing Gear ◽  
Killer Whales ◽  
Fishing Vessels ◽  
Long Line ◽  
Target Fish ◽  
Pilot Whales ◽  
Warm Temperate

Observers from the Australian Fisheries Management Authority worked on randomly chosen Japanese long-line vessels in the Australian Fishing Zone (AFZ) between 1980 and 1997. Observer reports (n = 451) were inspected for interactions or sightings of marine mammals. An operational interaction was defined as an activity or behaviour that involved direct contact between a marine mammal and fishing gear, bait, target fish or bycatch, or indications that the marine mammal was feeding. A sighting was defined as the recording of marine mammals that passed the vessel without changing course and/or did not appear to interact with the vessel or its gear. Observers witnessed 23 interactions and made another 44 sightings of marine mammals. A further 24 interactions and sightings were relayed by crew members. Killer whales were reported most frequently: most incidences of fish being damaged, taken or frightened away were attributed to them. Eleven marine mammals were caught: two died, seven were released, and the fate of two others was not recorded. Between 1991 and 1996, when observer coverage was 11.5% overall in the AFZ, the incidence of interactions was 1.71 per million hooks set. The estimated number of interactions in that seven-year period was 157 in the AFZ. Since 1997, the long-line fishery has been conducted by Australian vessels, primarily off the east coast of mainland Australia in warm-temperate waters. A higher proportion of interactions can be expected with killer whales and short-finned pilot whales in these waters, and fewer with seals.

scholarly journals A preliminary fish survey of the estuaries on the south-east coast of South Africa, Kei Estuary to Mdumbi: A comparative study

Water SA ◽  
2020 ◽  
Vol 46 (3 July) ◽  
Author(s):  
NC James ◽  
TD Harrison
Keyword(s):  
South Africa ◽  
Significant Relationship ◽  
East Coast ◽  
Multivariate Analyses ◽  
Fish Communities ◽  
Chemical Characteristics ◽  
The South ◽  
Physico Chemical ◽  
Biogeographic Region ◽  
Warm Temperate

A preliminary ichthyofaunal and physico-chemical survey of estuaries on the south-east coast of South Africa from the Kei Estuary to the Mdumbi Estuary was undertaken between October and November 1997. Twenty-seven (27) estuaries were surveyed along this stretch of coastline and these were grouped into three estuary types: small (< 10 ha) predominantly closed estuaries, moderate to large (> 10 ha) predominantly closed estuaries and predominantly open estuaries. Multivariate analyses revealed significant differences between predominantly closed estuaries and predominantly open estuaries in terms of both their physico-chemical characteristics and their fish communities. There was no difference between small and moderate to large predominantly closed estuaries.  A significant relationship was also observed between the physico-chemical characteristics of the estuaries and their fish communities.  The estuaries in the study area fall within the warm-temperate biogeographic region; temperate species dominated the fish communities of all the estuaries. This survey represents one of the few fish surveys undertaken along this little-studied section of the coastline. 

Role of decreased plasma volume in hematocrit alterations during incremental treadmill exercise in horses

1993 ◽  
Vol 265 (2) ◽  
pp. R404-R408 ◽  
Author(s):  
K. H. McKeever ◽  
K. W. Hinchcliff ◽  
S. M. Reed ◽  
J. T. Robertson
Keyword(s):  
Heart Rate ◽  
Plasma Volume ◽  
Exercise Test ◽  
Treadmill Exercise ◽  
Incremental Exercise ◽  
Blood Samples ◽  
Incremental Exercise Test ◽  
Relative Change

Six intact (IN) and six splenectomized (SP) mares were subjected to an incremental exercise test to examine the role of decreases in plasma volume (PV) in the changes in hematocrit (Hct) normally seen with exercise. Each horse underwent an incremental exercise test in which it ran on a treadmill up a fixed incline of 6 degrees. The test started at a speed of 4 m/s, and speed was increased 1 m/s each min until heart rate reached a plateau. Blood samples were obtained at rest and at the end of the 4, 5, 6, and 7 m/s steps of the exercise test. Resting PV was greater (P < 0.05) in the IN group (28.6 +/- 0.5 liters) compared with SP horses (22.7 +/- 2.2 liters). Exercise produced a significant increase in Hct in both groups of horses; however, the increases were greater (P < 0.05) at all exercise intensities in IN compared with SP horses. Hct increased rapidly during the first step (4 m/s) in the exercise test in the IN animals. After this, Hct increased slowly in IN horses, and values for the 5, 6, and 7 m/s steps paralleled the changes observed in the SP horses. Corrected Hct values were then used to calculate the relative change in PV. Exercise produced a significant decrease in PV in both groups of horses; however, there were no differences (P > 0.05) between the groups when IN horses (-13 +/- 3 and -18 +/- 2%) were compared with SP horses (-14 +/- 4 and -17 +/- 4%) at the 6 and 7 m/s steps of the exercise test.(ABSTRACT TRUNCATED AT 250 WORDS)

Physiologic limits to work in the heat and evaporative coefficient for women

1976 ◽  
Vol 41 (1) ◽  
pp. 71-76 ◽  
Author(s):  
E. Kamon ◽  
B. Avellini
Keyword(s):  
Heart Rate ◽  
Water Vapor ◽  
Inflection Point ◽  
Water Vapor Pressure ◽  
Mean Skin Temperature ◽  
Thermal Limits ◽  
Air Movement ◽  
Air Temperatures ◽  
Physiologically Based ◽  
Psychrometric Chart

Ten heat-acclimated females exercised seminude on a treadmill at 30% Vo2 max (M=152 W-m-2) under eight air temperatures (Ta) ranging from 30 degrees C to 52 degrees C. Each experiment involved 1 h of fixed and a 2nd h of progressively increasing water vapor pressure (Pw) with either air movement of 1 m-s-1 or still air. The equilibrium values of rectal temperature (Tre), mean skin temperature (Tsk),and heart rate (HR) reached in the 1st h were forced upwards in the 2nd h by the rising Pw. The critical Pw was defined by the Tre inflection point for each Ta. The loci of the critical Pw were used to delineate the thermal limits on the psychrometric chart and were used to derive the effective evaporative coefficient (Ke') applicable to the ambient capacity for evaporative cooling (Emax). The derived Ke' was 17.6 +/- 4.2 W-m-2 (mean +/- SD) for v0.6m-s-1. Isotherms constructed on the basis of the obtained Ke, Tsk, and sweating capacity were higher than the physiologically based Pw limits.

Experimental mixing of a north-temperate lake: testing the thermal limits of a cold-water invasive fish

2015 ◽  
Vol 72 (6) ◽  
pp. 926-937 ◽  
Author(s):  
Zach J. Lawson ◽  
M. Jake Vander Zanden ◽  
Colin A. Smith ◽  
Emily Heald ◽  
Thomas R. Hrabik ◽  
...  
Keyword(s):  
Cold Water ◽  
Thermal Sensitivity ◽  
Field Testing ◽  
Population Declines ◽  
Rainbow Smelt ◽  
Thermal Habitat ◽  
Thermal Thresholds ◽  
Adult Age ◽  
Intrapopulation Variation ◽  
Thermal Limits

Species’ thermal limits play a key role in determining spatial distributions and understanding their response to changing environments. Manipulation of thermal habitat is a potential avenue of exploration for management of invasive species such as the cold-water rainbow smelt (Osmerus mordax), which has adverse effects on native fish communities in central North American inland lakes. In an effort to test the thermal limits and selectively eradicate rainbow smelt, we experimentally mixed Crystal Lake, Wisconsin, USA, during summer of 2012 and 2013 to warm the hypolimnion and eliminate cold-water habitat. This whole-ecosystem manipulation allowed for field testing of published thermal thresholds reported for rainbow smelt. The rainbow smelt population responded to the thermal manipulation by exhibiting unexpected shifts in behavior, intrapopulation divergence in body condition, and significant population declines. Small individuals of each adult age-class tended to survive the manipulation, and the population persisted despite high mortality rates. Our results indicate a high degree of size-based intrapopulation variation in thermal sensitivity for this species. Our findings also raise questions regarding applicability of lab- and model-derived thermal limits to field scenarios, highlighting a need for further field evaluations of species’ thermal limits.

scholarly journals High-resolution modeling of thermal thresholds and multiple environmental influences on coral bleaching for regional and local reef managements

2017 ◽  
Author(s):  
Naoki H. Kumagai ◽  
Hiroya Yamano ◽  
Keyword(s):  
High Resolution ◽  
Uv Radiation ◽  
Coral Bleaching ◽  
Environmental Influences ◽  
Thermal Indices ◽  
Water Turbidity ◽  
Thermal Index ◽  
Thermal Thresholds ◽  
Cooling Effects ◽  
Global And Local

AbstractCorals are one of the communities most threatened by global and local stressors. Excessive summer sea temperatures can cause coral bleaching, resulting in decreases in living coral coverage. Coral bleaching may begin with rising sea temperatures, although the widely used threshold of 1 °C over the local climatological maximum sea temperature has been reconsidered. In this study, we refine thermal indices predicting coral bleaching at high resolution (1 km) by statistically optimizing the thermal threshold and multiple environmental influences on bleaching, such as ultraviolet (UV) radiation, water turbidity, and cooling effects on corals. We use a dataset of coral bleaching events observed during 2004–2016 in Japan derived from the Web-based monitoring system, the Sango (Coral) Map Project, aiming at regional to local conservation of Japanese corals. We show how the ability to predict coral bleaching is improved by the choice of thermal index, statistical optimization of thermal thresholds, usage of multiple environmental influences, and modeling methods (generalized linear model and random forest). After optimization, the differences among the thermal indices in the ability to predict coral bleaching were slight. Among environmental influences, cooling effects, UV radiation, and water turbidity, in addition to a thermal index, well explain the occurrence of coral bleaching. Prediction based on the best explanatory model reveals that recent Japanese coral reefs are experiencing bleaching in many areas, although we show a practical way to reduce bleaching frequency significantly by screening UV radiation. Thus, our high-resolution models may provide a quantitative basis for the management of local reefs under current global and local stressors. The results of this study may be useful to other researchers for selecting a predictive method according to their needs or skills.

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