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1.
J. S. Claytont 《新西兰海洋与淡水研究杂志》2013,47(1):89-94
Fluctuations in water level and the growth of the introduced exotic Lagarosiphon major (Ridley) Moss have significantly influenced the submerged vegetation of Lake Rotoma over the period 1973–80. Low lake levels temporarily reduced the proportion of native vascular plants by removing available shallow‐water habitats through erosion, siltation, or desiccation. High lake levels have allowed native vascular plants to re‐establish from seed and rhizomes. Fluctuations in water level appear to have reduced the long‐term replacement of native species by L. major, which has none the less spread progressively around the lake. Water‐level fluctuations enhanced its rate of fragmentation, and thus its dispersal and establishment. The annual increase in the proportion of L. major has been primarily at the expense of the shallow‐water characean algae, but also partly by competitive displacement of native vascular plants. The southwest inlet of Lake Rotoma had an exceptionally high plant density, with up to 3518 g/m2 dry weight of L. major (believed to be a world record for submerged plant biomass); this is attributed to local enrichment and protection from wave exposure. 相似文献
2.
A preliminary scuba survey of oligotrophic Lake Rotoma in 1972 revealed a vegetation mainly composed of native hydrophytes in which exotics were at an early stage of colonisation. In 1973 the presence of species was recorded in 5708 quadrats (625 cm2) at 1 m intervals along a total of 50 line transects placed systematically around the lake. Water depth was measured, and quadrat cover and substrate type were subjectively estimated. Species frequency calculations showed that the dominant vegetation pattern was a characean meadow of Chara fibrosa f. acanthopitys (A.Br.) R.D.W., Nitella leptostachys var. leonhardii (R.D.W.) R.D.W., and N. pseudoflabellata var. mucosa (Nordst.) Bailey. The charophytes extended over a depth range of 1–17.5 m on a wide variety of substrates and gradients. Native vascular plants were absent from many transects, and had a depth range only from 0 to 4.5 m, with most occurring above 3.5 m. The Low Mixed Community, found in shallow water less than 1.25 m in depth at the northeast end of the lake, provided this area with a high species diversity. Exotic hydrophytes had established in many areas around the lake. The distribution of Lagarosiphon major (Ridley) Moss and Elodea canadensis Michx. appeared to coincide with boating access and fallen submerged trees over a depth range of 0–6.0 m, although much of the available habitat had not yet been exploited. Emergent species were most abundant within the southwest inlet and also in the lagoons surrounding the lake where sheltered conditions and shallow gradients prevail. 相似文献
3.
Five plant communities in Lake Rotoiti, North Island, New Zealand (38° 02’ S, 176° 24’ E) are described. In shallow water (0–2 m depth) partly protected from the prevailing westerly winds, some indigenous species form characteristic mounds. From 2 to 6 m depth the exotic macrophyte Lagarosiphon major (Ridley) Moss is the dominant and forms dense beds which appear to have completely replaced any native vegetation. Elodea canadensis Michx., a longer‐established exotic, may form a minor component of this zone, but may become the dominant species in water above and below the Lagarosiphon zone. Lagarosiphon appears to be primarily restricted to silty sand, but on pure silt areas it is replaced by Elodea and/or Nitella hookeri A. Braun. These zonations are probably static rather than successional. On underwater cliff faces and boulder shores a seasonal succession of algae was the major vegetation. Only filamentous cyanophytes grew within 1–2m of geothermal springs in the lake. 相似文献
4.
The distribution of seven submerged aquatic pest plants is reported. Lake vegetation surveys recorded pest plants in 27.9% of 344 lakes, with two species co‐occurring in 5.8%, and three species in 2.6% of lakes. Egeria densa was most frequent (15.4% of lakes), followed by Ceratophyllum demersum (9.0%), Lagarosiphon major (7.3%), and Utricularia gibba (5.5%). Spread since 2000 has continued for five pest plants, with 34 lakes invaded by U. gibba over 2004–08 alone. Early regional sites in proximity to human population centres were likely plant liberations and numerous potential founder colonies remain in garden ponds. Human activities were important for inter‐lake dispersal, with the exception of bird‐dispersed U. gibba. Significant lake associations between pest plants, and with presence of six exotic fish species, suggest common dispersal pathways and similar introduction risks. Therefore, predictions of future spread should be possible based on sources, dispersal pathways, and identifying key risk factors for lakes. 相似文献
5.
6.
Landlocked sockeye salmon (Oncorhynchus nerka), ranging in fork length (FL) from 105 to 313 mm, were captured in fine‐mesh gill nets set in the limnetic zone of the Waitaki hydro lakes (44° 30′ S, 170° 10’ E) in the South Island, New Zealand. A total of 443 stomachs was examined and the frequency of occurrence, volume and weight of prey items calculated. In the Ahuriri Arm of Lake Benmore the principal food (54% by weight) was zooplankton (Boeckella dilatata) whereas in the Haldon Arm of Lake Benmore it was larval and juvenile common bullies (Gobiomorphus cotidi‐anus) (73% by volume). In Lake Waitaki in winter, salmon had eaten insects (43% by volume) with smaller amounts of snails (Potamopyrgus antipo‐darum, 23%) and bullies (24%). In Lake Ohau adult insects may be an important food. There were also variations in diet with season and fish size. The stomachs of 147 brown trout (Salmo trutta) and 181 rainbow trout (S. gairdnerii) caught in the same gill nets were also examined. In contrast to sockeye salmon stomachs they contained negligible amounts of zooplankton (< 1% by weight) and large amounts of aquatic insects (50–58% by weight in the Ahuriri Arm of Lake Benmore). Comparisons with juvenile sockeye salmon and kokanee in North American lakes are made. The impact of introductions of sockeye salmon into other New Zealand lakes is discussed. 相似文献
7.
The limnology of Lake Rerewhakaaitu (36°18'S, 176° 30'E) was studied at various intervals between 1971 and 1974; comparisons were made between the main lake (area 6.32 km2, mean depth 7 m, maximum depth 15 m), and the smaller (0.15 km2) and deeper (mean depth 15 m, maximum 31 m) crater which are connected by a narrow, 1 m deep channel. The main lake was usually homothermal, although temporary stratification periodically occurred, and the oxygen content of the deeper water could be as low as 2 g.m‐3. The crater showed strong thermal and chemical stratification persisting well into the winter. Its heat budget and other factors related to lake stability are compared with those of some other New Zealand lakes. The failure of the crater to become fully re‐oxygenated during its brief period of homothermy is believed to be related to its morphometry, since the amount of phytoplankton did not appear to be great enough to explain the low levels of dissolved oxygen in the hypolimnion. The hypolimnetic oxygen deficit in 1973–74 was 0.038 mg. cm‐2.day‐1. Qualitatively the phytoplankton, usually dominated by desmids, was characteristic of oligotrophic waters, but quantitatively the main lake could be rated as mesotrophic. Differences were also found in the abundance of zooplankton between the crater and the main lake: there were usually more Bosmina but considerably fewer Ceriodaphnia in the main lake which had greater numbers of Piona. Adult Calamoecia were generally more abundant in the crater. 相似文献
8.
In two small monomictic lakes near Queenstown, South Island, New Zealand, algal associations characteristic of eutrophic waters were present throughout most of the period from December 1969 to February 1972. In Lake Hayes, five of the six algal genera which were recorded in the plankton in 1948–50 were still present, but Anabaena appeared to have increased. Blooms of A. flos‐aquae which were not recorded 20 y ago (Jolly 1952) occurred in the lake in the three summers of this study and in winter of the second year. Melosira granulata dominated the plankton in winter; at other times of the year Closterium aciculare, Cyclotella kuetzingiana, and Staurastrum spp. were dominant. In Lake Johnson the major algae differed from one year to another. Blooms of Anabaena flos‐aquae formed during the first two summers but were absent in the third, when Closterium aculum var. variabile was dominant. Peridinium cinctum was abundant throughout the first year, especially in December 1969 and October 1970, when concentrations of more than 1000 cells per ml occurred at the surface. During autumn and winter of the second year, Staurastrum bibrachiatum dominated the plankton. In both lakes micro‐algae were abundant in late spring and early summer. In winter when the lakes were isothermal, algae were distributed fairly uniformly with depth. During the period of thermal stratification, algae were mainly confined to the epilimnion. Although green algae and diatoms were usually dispersed fairly uniformly throughout this zone, Cryptomonas and Peridinium were often concentrated at a certain depth. In Lake Johnson in late summer 1971, a layer of purple photosynthetic bacteria, of which concentrations of 0.5–1.3 × 10° cells per ml were recorded, was present at a depth of 7–8 m. Algae were more abundant in summer than in winter in both lakes. The mean standing crop of algae for the trophogenic zone of Lake Hayes was 6000 cells per ml, and a maximum crop of 65 000 cells per ml was recorded in December 1971 during an Anabaena bloom: the mean volume of phytoplankton was 1.93 mm3 per litre for the trophogenic zone with a maximum of 7.49 mm3per litre in January 1970 when Anabaena and Peridinium were abundant. In Lake Johnson the mean number of algae in the trophogenic zone was 11000 cells per ml and the mean volume of phytoplankton was 9.37 mm3 per litre: a maximum volume of 33.12mm3 per litre was recorded in October 1970 when Peridinium was abundant. 相似文献
9.
洱海生态环境恶化及综合治理对策研究 总被引：7，自引：0，他引：7
由于７０年代中期西洱河电站建成发电引起洱海水位下降，加之流域植被破坏，水土流失及酷渔监捕，不合理引种等原因，使洱海生态环境发生了变迁。湖泊面积缩小５％左右，容积减少１４％左右；浮游动植物，底栖动物的种群结构，数量发生明显变化；土著鱼种类和数量急剧减少；水在维管束植物覆盖面积达２７％，生物总量达５６．３万ｔ。为此提出保持水位植树造林，控制点，面源污染，适度捕捞及加强管理等综合治理对策。 相似文献
10.
高原湖泊溶解有机质的三维荧光光谱特性初步研究 总被引：9，自引：0，他引：9
提要近年来,荧光光谱技术被广泛应用于研究天然水体中溶解有机质(Dissolved Organic Matter,DOM)的物理化学特性。为了理解高原湖泊中DOM的组成、荧光光谱特性及其在湖泊水体中的垂直分布情况,作者利用荧光发射光谱、三维荧光光谱研究云贵高原湖泊红枫湖和百花湖中的DOM。结果显示,高原湖泊DOM主要表现为类富里酸荧光,包括可见区和紫外区两种类型的荧光峰,各种天然水体中都有报道的类蛋白荧光在红枫湖DOM中并不明显,而在百花湖DOM中则有较强的类蛋白荧光。溶解有机质所含三种类型荧光峰(PeakA:紫外区类富里酸荧光峰;PeakB:可见区类富里酸荧光峰;PeakC:类蛋白荧光峰)的荧光强度与溶解有机碳之间没有明显的线性相关关系,可能与高原湖泊水体pH值、DOM在湖泊不同深度由于受到光降解、微生物降解等作用存在差异等因素有关。与有机质结构和成熟度有关的荧光峰比值r(A,C)在1.40—2.09范围内,红枫湖南湖、百花湖DOM样品的r(A,C)值随着水体深度有下降的趋势,而红枫湖北湖DOM的r(A,C)值则随着水体深度有较大起伏,揭示了高原湖泊水体中DOM的结构以及分布情况存在差异。另外,r(A,C)值与pH之间具有良好的正相关关系,其相关系数红枫湖南湖DOM为0.95,百花湖两个采样点DOM分别为0.67、0.75,而红枫湖北湖DOM则显示出一定的负相关性(R2=0.45)。 相似文献
11.
千岛湖水温垂直分层的空间分布及其影响因素 总被引：1，自引：0，他引：1
湖泊热力分层及热力循环深刻影响深水湖泊生态系统。随着全球气候变暖,湖泊热力过程会发生显著变化。作为深水水库型湖泊,千岛湖的热力过程与水环境的变化紧密相连,为了分析千岛湖水体水温、湖泊热力分层参数(温跃层深度、厚度和强度)的分布,探讨温跃层深度与水温、水体透明度以及水深之间的关系,本文根据2014年7月份与2015年5月份对千岛湖全湖60个采样点的水体理化指标的垂向分布调查数据,计算得到千岛湖热力分层参数,进而分析其时空分布特征及主要影响因素。结果表明,千岛湖水体水温垂直分布呈现正温分布,春夏季全湖范围内均存在不同程度的温度分层现象,温跃层深度、厚度和强度均从上游河口向下游敞水区逐步增大,这种空间变化的趋势在7月份比5月份更显著。水温、透明度和水深是影响温跃层深度的主要因素。夏季湖泊热力分层稳定期温跃层深度与表层水温(0—2m)存在显著负相关关系,与透明度和水深存在正相关关系。 相似文献
12.
Oxygen consumption was estimated for two eutrophic New Zealand lakes using a simple 2‐layer model, from estimates of net changes in oxygen, phytoplankton photosynthesis, inflow and outflow, diffusion, eddy diffusion, and changes in the depth of the thermocline. Of the total oxygen consumption, 75–85% occurred in the epilimnia. Epilimetic oxygen consumption per m3 and per m2 in Lake Johnson were higher than in Lake Hayes, reflecting known differences in the trophic status of the lakes, but estimates for the hypolimnia of the two lakes were similar. Daily hypolimnetic areal deficits were sensitive to both the depths and time intervals chosen. In the epilimnia, monthly oxygen production by photosynthesis averaged 1.1 and 1.8 times the initial oxygen content in Lakes Hayes and Johnson respectively. Diffusion appeared to be of similar magnitude to photosynthesis in the isothermal period, but was less important during stratification. Losses to the hypolimnia by eddy diffusion were less than 10% of photosynthesis. Photosynthesis in the hypolimnia contributed 30–40% of the oxygen consumed there and eddy diffusion supplied a further 20%. In Lake Johnson a 3–5 m stratum of water in the metalimnion became anoxic for 2–3 months each summer while there were still up to 5.2 g.rer3 of oxygen remaining in the hypolimnion. Metalimnetic anoxia is attributed largely to oxygen consumption in situ, resulting from the highly eutrophic state of the lake and intense thermal stratification. Zooplankton respiration accounted for less than 10% of the maximum net decline in metalimnetic oxygen in 1970–71, but was more important in the other 2 years. Changes in the oxygen content of the hypolimnion indicate that Lake Hayes has become more eutrophic since 1954–55. In Lake Johnson low oxygen concentrations at the autumn overturn (<5 g.m‐3) represent a threat to the trout population. 相似文献
13.
The comparative limnology of some New Zealand lakes 总被引：1，自引：1，他引：0
V. Hilary Jolly 《新西兰海洋与淡水研究杂志》2013,47(2):214-259
The morphometry, environmental conditions, and some physical and chemical data are given for twenty‐four New Zealand lakes: seven are in the southern part of the South Island, the others, excluding Lakes Waikaremoana and Waikareiti, are in the “thermal region” of the central North Island. These lakes form two separate groups and include the largest and deepest lakes in both islands. The lakes in which stratification was established were found to belong to the class known as warm monomictic Two lakes, Rotorua and Rotoehu, were found to be homothermous throughout the year. Open water surface temperatures did not exceed 23°c in the North Island lakes or 19°c in the South Island, and minimum temperatures recorded were 7°c in the northern lakes and 5°c in the southern. In deep lakes the range of temperature was much less: Wakutipu had a range of 16–8.85°c. The disappearance level of a Secchi disc varied from 18 m (Lake Taupo) to 0.8 m (Lake Rotongaio). The transparency of the water in the glacial and volcanic lakes was comparable to that of similar lakes in other parts of the world. It was found that total ions, measured by the ion‐exchange resins reached high concentrations in lakes fed by thermal waters: Rotomahana 14.32m.e./l. By contrast Tikitapu, a seepage lake, had the low concentration of. 0.28m.e./l, and Wakatipu, a glacial fed lake, a concentration of O.58m.e./1. The pH range was 8.1–5.8, the lowest value being in Tikitapu, a volcanic lake. Slightly lower pH values were recorded in the bottom waters of lakes when stratified. Lakes were usually supersaturated with oxygen at the surface, and only a few small lakes showed a hypolimnial deficiency. Silica and phosphate were found in high concentrations in some thermal lakes but nitrogen in the forms measured, was found to be low. 相似文献
14.
Clive Howard‐Williams Karen Law Connie L. Vincent John Davies Warwick F. Vincent 《新西兰海洋与淡水研究杂志》2013,47(4):583-597
Lake Waikaremoana, the North Island's deepest lake (248 m), lies in a natural forested catchment, but the lake itself has been modified for hydro‐electric power generation and by the introduction of trout, smelt, and adventive aquatic plants. The lake is a warm monomictic water body of low conductivity (82 μS cm‐1) and a high seasonal water column stability. The waters are oligotrophic, with epilimnetic dissolved reactive phosphorus concentrations typically < 1 mg m‐3. The concentration of NO3‐N is seasonally variable but generally high in winter and spring with maximum epilimnetic values approaching 70 mg m 3. This contrasts with other central North Island lakes. Horizontal variability in surface chlorophyll a is low as are the absolute values (< 1–2 mg m‐3). A notable feature is the formation of a deep chlorophyll maximum within the metalim‐nion comprised largely of Sphaewcystis schweteri as opposed to diatoms and flagellates which normally dominate the epilimnion. Vascular macro‐phytes (maximum biomass 659 g m2 dry weight) extended to 9 m and characeans (maximum biomass 447 g m2dry weight) to 16 m. Total phyto‐plankton primary production was calculated as 4524 tCy‐1 and macrophyte production as 578 t C y‐1. The proportion of macrophyte to phy‐toplankton production (0.14) is higher than in the other deep lakes of the central North Island. 相似文献
15.
Abstract Stomach contents of Gobiomorphus cotidianus,Retropinna retropinna, Gambusia affinis, and Anguilla australis were compared between two shallow lakes in the lower Waikato River basin, to examine the relationship between turbidity and diet. Lake Waahi and the south arm of Lake Whangape had been turbid (20–40 g suspended solids (SS) m?3) and devoid of submerged macrophytes since the late 1970s and early 1980s, respectively. The main basin of Lake Whangape had been generally clearer (5 g SS m?3) with dense beds of submerged macrophytes, but at the time of sampling (1987) water clarity had deteriorated (> c. 10 g SS m3) and submerged macrophytes had declined. The mysid Tenagomysis chiltoni was an important prey for all species of fish from turbid water bodies but was less important in stomachs of fish in the main basin of Lake Whangape. Apparently, mysids were not an important prey in Lake Waahi before it became turbid. Chironomid larvae and pupae dominated the diets of small fish in the main basin of Lake Whangape. Fish and mysids were the most important prey of shortfinned eels in both lakes, with mysids most important in Lake Waahi. High mysid densities in the turbid water bodies provide an alternative food resource apparently compensating for those lost by fish when water clarity declined and submerged macrophytes collapsed. 相似文献
16.
Sampling of kōura (freshwater crayfish Paranephrops planifrons) to assess population abundance and structure in lakes is often difficult or impractical because of the absence of representative methods. The tau kôura is a traditional Maori method used to catch kôura in central North Island lakes by placing whakaweku (bundles of bracken fern Pteridium esculentum) on the lake bed that kôura then colonise. It has advantages as a monitoring tool over conventional methods, such as baited traps and dive surveys, as it samples all kôura size classes, can be used in turbid waters and at a wide range of depths, and does not require expensive equipment or specialised expertise (e.g., SCUBA). We demonstrate its use to monitor kôura populations in Lake Rotoiti (mean depth 32 m), North Island, New Zealand. Application of the method allowed differences in population size structure to be distinguished between a shallow and a moderate depth site within Lake Rotoiti and to discern seasonal breeding patterns. 相似文献
17.
于1987年7月和1989年7,8月对乌伦古湖水生植被及其生态环境作了调查。结果表明,水位回升扭转了水生植被的退缩趋势,新生滩地上次生植物群落的形成使得Ⅳ区以北的水生植被总面积由1985年的813ha增加到1989年的4365ha,总储量由7700t增加到41750t。芦苇占现有植被区面积的81％。和总储量的68％。现有水生植被正处在迅速演变之中,随着植被的发育,植被总面积将会减小到3500ha左右,但总储量将会逐年增加。植被现有生产力约58955t,对渔业和环境十分重要,应加强对其开发利用。 相似文献
18.
B. P. Penlington 《新西兰海洋与淡水研究杂志》2013,47(4):349-355
The presence of suitable gravel size alone can stimulate female rainbow trout (Salmo gairdneri) to excavate nests for spawning on the shores of Lake Rotoma. Emergent fry result from lake‐shore spawning, and could contribute significantly to the trout fishery in Lake Rotoma. Lake‐shore spawning could be enhanced by the use of stable artificial spawning beds that have adequate depth and appropriate sizes of gravel. 相似文献
19.
P. M. Hine 《新西兰海洋与淡水研究杂志》2013,47(2):189-195
Myxidium zealandicum Hine, 1975 was recorded from several tissues in New Zealand freshwater eels. The gills were the most frequent site of infection, but spores also matured on the gill arch, in the skin, and occasionally in the urinary and swim bladders. Thus M. zealandicum is a histozoic species that may have evolved from a coelozoic form. Variation in spore size (8.0–11.5 jam) was found in relation to site of infection; variation in the number and arrangement of valve striations was also observed. Deposition of fibro‐blasts occurred at all sites of sporogony, except among the goblet cells of the epidermis. The small size (6.0–10.5μm) of unstriated spores occurring with normal spores in the gills of eels from Lake Otomangakau appeared to be related to the size of the cysts in which they occurred, and to the host Anguilla dieffenbachii. 相似文献
20.
We reviewed lakes in New Zealand reported to have undergone regime shifts between macrophyte‐dominated clear water states and de‐vegetated, turbid states. Regime‐shifting lakes (RSLs) occurred along a wide latitudinal gradient. We obtained catchment land‐use data as well as data on the occurrences of introduced (non‐indigenous) macrophytes and herbivorous and benthivorous fish for the 37 RSLs and for 58 lakes with similar maximum depths and climates, but which had not been reported to have undergone regime shifts. All RSLs had a maximum depth <20 m and mean annual surface air temperature between 9 and 16°G Regime shifts were positively related to the percentage of the catchment in pasture and negatively related to the percentage of the catchment in forest. The occurrences of the introduced macrophyte Egeria densa and the introduced fish, Ameiurus nebulosus (catfish), Carassius auratus (goldfish), Scardinius erythrophthalmus (rudd), Cyprinus carpio (koi carp), and Tinca tinca (tench), were significantly correlated to regime shifts in lakes. Although the presence of other introduced aquatic macrophytes was not significantly correlated with RSLs, the number of exotic fish taxa present in lakes was strongly positively correlated with increasing prevalence of regime shifts. The strength of the correlations between land use and introduced species versus regime shifts illustrates a number of factors which could be managed to reduce the susceptibility of lakes to regime shifts and to restore lakes that have become de‐vegetated. Our findings also suggests that regime shifts in lakes were unlikely to have been common in New Zealand lakes before anthropogenic deforestation and introductions of introduced aquatic taxa. 相似文献