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The effects of exposure to ultraviolet radiation (UVR), 280–400 nm, in different life histories and development stages of the kelps, Lessonia nigrescens and L. trabeculata, collected in the south-east Pacific coast (30°S) were evaluated in the laboratory. Germination and viability (motile zoospores, settled spores), diameter of the primary cell of the gametophytes, percentage of female gametophytes, fertility and sporophytes production were measured after exposure to three radiation treatments (PAR; PAR + UVA; PAR + UVA + UVB). The effects of UVR in young sporophytes (diploid stage) were evaluated as changes in maximal quantum yield of chlorophyll fluorescence of photosystem II (PSII) (F
v/F
m). A significant decrease in all variables was observed for the treatment that included UVB (PAR + UVA + UVB) after 2 and 4 h of exposure, in relation to the control. The motile spores were more sensitive to UVR exposure compared to settled spores and gametophytes, suggesting that along with an increase in ontogenetic development; there is an increase in the tolerance to UVR. In addition, it was observed that early stages of the intertidal L. nigrescens were more tolerant to UVR compared to the subtidal L. trabeculata. These results allow initially to infer that UVR may be regarded as an important environmental factor influencing the upper limit of distribution of these species, mainly through its detrimental effects on the early stages of the life cycle. 相似文献
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Large quantities of floating macroalgae are traveling in coastal waters of the SE Pacific and in other temperate climate zones.
While afloat, these algae are potentially exposed to full solar radiation, including UVA and UVB, which can have profound
effects on their physiological and growth performance. Latitudinal variations in UV-radiation (UVR) are hypothesized to affect
floating algae differently with higher impacts at low latitudes than at high latitudes. In addition, UVR together with grazing
might accelerate the demise of floating kelps. This hypothesis was tested with outdoor laboratory experiments in which sporophytes
of the giant kelp Macrocystis pyrifera (L.) C. Agardh were exposed to a combination of different UVR regimes (PAR only, PAR + UV) and grazing at three sites along
the Chilean coast (20°S, 30°S, and 40°S). A latitudinal trend in irradiance was detected with increasing values from 40°S
to 20°S. Surprisingly, floating M. pyrifera responded with a high acclimation potential within this latitudinal UVR gradient. At 20°S, floating kelps were slightly sensitive
to UVR, which was reflected in reduced blade growth. At 30°S, physiological responses were hardly affected by the prevailing
irradiance but sporophyte growth and thus persistence mainly depended on the presence or absence of amphipod grazers. At high
latitudes, grazing had only minor impacts on algal biomass and blade growth, and kelps thrived well under all tested environmental
conditions. Overall, our results reveal that floating M. pyrifera was only slightly affected by UVR and that sporophytes can efficiently acclimate over a latitudinal UVR gradient that spans
from 20°S to 40°S. Given this high acclimation potential, we suggest that these (and possibly other) positively buoyant algae
are important dispersal agents over a wide range of temperate latitude conditions. 相似文献
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The Horqin sandy rangeland of northern China is a seriously desertified region with a fragile ecology. The sandy alluvial and aeolian sediments have a coarse texture and loose structure and are therefore vulnerable to damage caused by grazing animals and wind erosion. We investigated whether grazing exclusion could enhance ecosystem carbon (C) and nitrogen (N) storage and thereby improve overall soil quality. We compared soil properties, C and N storage in biomass (aboveground and below-ground), and the total and light fraction soil organic matter between adjacent areas with continuous grazing and a 12-year grazing exclosure. The soil silt?+?clay content, organic C, total Kjeldahl N, available N and K, and cation-exchange capacity were significantly (P?0.05) greater in the exclosure. We found that to a depth of 100?cm, the exclosure plots had greater light fraction C storage (by 267.2?g?m(-2)?=?73.3?%), light fraction N storage (by 16.6?g?m(-2)?=?105.7?%), total soil C storage (by 1174.4?g?m(-2)?=?43.9?%), and total N storage (by 91.1?g?m(-2)?=?31.3?%). Biomass C and N storage were also 205.0 and 8.0?g?m(-2) greater (154.8 and 181.8?%, respectively). The increase was greatest in the light fraction organic matter and biomass and decreased with increasing depth in the soil. The results suggest that light fraction C and N respond more rapidly than total soil C and N to grazing exclusion and that vegetation recovers faster than soil. Our results confirmed that the degraded sandy rangeland is recovering and sequestering C after the removal of grazing pressure. 相似文献
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The bull kelp Durvillaea antarctica is a common floating alga in the southern hemisphere, but despite the ecological and biogeographic importance of kelp rafts, little is known about the responses of detached kelps to the conditions at the sea surface. The morphological, physiological and reproductive performances of D. antarctica rafts in the Coastal System of Coquimbo, Chile (CSC, ~30°S), were examined during winter and summer of two successive years (2010/11 and 2011/12). Epibionts (Lepas spp.) that only attach to floating objects were used as indicator for the floating time of kelp rafts. Photosynthetic efficiency and reproductive maturity of both benthic and floating algae varied seasonally, with a stronger decrease in summer than in winter. Blade size (measured as weight proportion of kelp individuals), phlorotannin concentrations and antioxidant activities were lower in floating than in benthic algae. Environmental conditions and floating time affected the blade tissues, with stronger negative effects during summer. These results confirm that floating persistence of D. antarctica in the CSC is suppressed during the summer months, which indicates that the dispersal potential of this (and other) floating algae varies seasonally. 相似文献
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Lars?GutowEmail author Jeremy?D.?Long Osvaldo?Cerda Ivan?A.?Hinojosa Eva?Roth?usler Fadia?Tala Martin?Thiel 《Marine Biology》2012,159(1):141-149
Many small marine herbivores utilize specific algal hosts, but the ultimate factors that shape host selection are not well
understood. For example, the use of particular microhabitats within algal hosts and the functional role of these microhabitats
have received little attention, especially in large algae such as kelps. We studied microhabitat use of the herbivorous amphipod
Peramphithoe femorata that inhabits nest-like domiciles on the blades of giant kelp Macrocystis pyrifera. The vertical position of nest-bearing blades along the stipe of the algal thallus and the position of the nests within the
lateral blades of M. pyrifera were surveyed in two kelp forests in northern-central Chile. Additionally, we conducted laboratory and field experiments
to unravel the mechanisms driving the observed distributions. Peramphithoe femorata nests were predominantly built on the distal blade tips in apical sections of the stipes. Within-blade and within-stipe feeding
preferences of P. femorata did not explain the amphipod distribution. Amphipods did not consistently select distal over proximal blade sections in habitat
choice experiments. Mortality of tethered amphipods without nests was higher at the seafloor than at the sea surface in the
field. Nests mitigated mortality of tethered amphipods, especially at the seafloor. Thus, protective microhabitats within
thalli of large kelp species can substantially enhance survival of small marine herbivores. Our results suggest that differential
survival from predation might be more important than food preferences in determining the microhabitat distribution of these
herbivores. 相似文献
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Christine C. Nguyen Cody N. Hugie Molly L. Kile Tala Navab-Daneshmand 《Frontiers of Environmental Science & Engineering》2019,13(3):46
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随着内蒙古自治区经济的飞速发展,带来了一系列的环境风险问题。自治区也应该建立与之相配套的应急监测预警体系,本文着重介绍了该体系建设的相关内容。 相似文献
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