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1.
The variability in water quality of urban runoff was assessed by comparing the concentration distributions and variations of various parameters over storm events in three catchments. The parameters chosen assessed nutrient, total oxygen demand, sediment, and toxic metal levels. Two catchments were located in Wairau Valley, Takapuna, Auckland. The smaller (1.49 km2), with residential/commercial landuse, formed part of the larger (11 km2) with predominantly residential/industrial/developing land. The third was a 1.14 km2 residential catchment in Hillcrest, Hamilton. The greatest dissimilarity occurred between the Hillcrest and the two Auckland catchments. Concentrations of suspended solids, total phosphorus, dissolved reactive phosphorus, Cr, Ni, and Zn were significantly higher in the Auckland catchments, whereas chemical oxygen demand, organic nitrogen, Pb, and volatile suspended solids were not significantly different from Hillcrest. NH4 + levels were higher in Hillcrest. Storm flows diluted NO3 ‐ concentrations in Hillcrest but increased NO3 ‐ concentrations in the Auckland catchments, resulting in comparable levels in all three catchments. It is proposed that most of the differences are attributable to higher specific flows and subsoil erosion in the Auckland catchments coupled with dissimilarities in soil concentrations and characteristics. The differences in the variation of NO3 ‐ concentrations were probably because of septic tank seepage in the Hillcrest catchment. The largest catchment differed from the two smaller catchments in having higher Cu and slightly lower TN and NO3 ‐ levels. All three catchments showed some similarities: Pb, Zn, and probably Cu and Cd were clearly enriched in the suspended sediment over background soil levels, and P, organic matter (COD, ON, VSS), Cr, and Ni were not enriched. It was concluded that geographical differences were more important in determining stormwater quality than urban infrastructure.  相似文献   

2.
Population dynamics of crayfish (Paranephrops planifrons White) in streams draining native forest and pastoral catchments, Waikato, New Zealand, were investigated from September 1996 to July 1998. Crayfish densities were generally greater in native forest streams because of high recruitment over summer, but varied greatly between streams in both land uses. Peak densities in summer were 9 crayfish m‐2 in native forest and 6 crayfish m‐2 in pasture streams, but peak biomass in summer was much greater in pasture streams. Mark‐recapture data showed that crayfish, particularly juveniles, in pasture streams grew faster than in native forest streams, through both greater moult frequency and larger moult increments. Females reached reproductive size at c. 20 mm orbit‐carapace length (OCL) after their first year in pasture streams, but after 2 years in native forest streams. Annual degree days >10°C appeared to explain the differences in the timing of life cycles. Estimates of annual crayfish production (range = 0.8–3.4 g dry weight m‐2 year–1) were similar in both land uses, and P/B ratios were between 0.95 and 1.2. Despite deforestation and conversion to pasture, crayfish in these Waikato hill‐country streams have maintained similar levels of annual production to those in native forest streams, although juvenile growth rates have increased and longevity has decreased.  相似文献   

3.
Measurements were made of suspended sediment (SS), volatile suspended solids, dissolved organic carbon (DOC), nitrogen (N) and phosphorus (P) concentrations, turbidity, black disk visibility, pH, alkalinity, and temperature, at monthly intervals for 2–5 years on nine streams draining catchments with pasture, pine plantation, and native forest land uses. Stream flow and flow‐weighted concentrations of SS, N, and P were also measured for up to 2 years from pasture, native forest, and mixed land‐use catchments enabling calculation of export (kg ha‐1 yr‐1). During 1996–97, export from the pasture stream was 2.5‐ to 7‐fold higher for SS (988), total P (1.50), total Kjeldahl N (5.65), nitrate N (4.37), and ammoniacal N (0.34) than from the stream draining native forest. In contrast, export of DOC (25.5) and dissolved reactive P (DRP) (0.25) from the pasture stream were within 20% of the native stream's values. Export of SS and nutrients (except DRP) from the pasture catchment was 4‐ to 15‐fold higher during the winters of 1995 and 1996 than winter 1997 when rainfall was half the normal level. Streams draining native forest had lower temperature, sediment, and nutrient concentrations (except DRP), and higher water clarity, than those draining pine forest and pasture. A pine/scrub stream had the highest SS and turbidity and lowest DRP, pH, and alkalinity. Pasture streams had the highest concentrations of all N species (geometric means 2‐to 4‐fold > native), total P, and DOC, and also showed the greatest variation in water quality attributes in relation to season and flow. The influences of land use were attributable to differences in both source materials of sediment and nutrients available for transport and changes in rates of in‐stream processing.  相似文献   

4.
Abstract

Phosphorus and nitrogen were measured in stream run‐off from the four catchments of the Taita Experimental Basin (41° 11′ S, 174° 58′ E). The land is used as exotic conifer forest, native forest, and hill pasture. Multiple regression analysis was used to estimate chemical losses per unit area in floods and at low flows.

At low flows, the hill pasture (fertilised with lime at 630 kg·ba?1·y?1, and superphosphate at 380 kg·ha?1·y?1) tended to lose more phosphorus and nitrate than the forested land, but differences were small, and not always significant. During large floods, the hill pasture (No. 5 Catchment) lost about 3 times as much reactive phosphate and 2–5 times as much total phosphorus as the forested land, and 130–190 times as much nitrate as land in the Exotic Forest and Native Forest 2 Catchments. Nitrate losses from land in the No. 4 Catchment (mainly native forest) were as high as those from the hill pasture, so high nitrate loss is not associated solely with agriculture.

Losses of total phosphorus via the catchment streams were estimated as: No. 5 Catchment (hill pasture), 293 g·ha?1·y?1; Native Forest 2 Catchment, 201 g·ha?1·y?1; No. 4 Catchment, 124 g·ha?1·y?1; Exotic Forest Catchment, 71 g·ha?1.y?1. Nitrate‐N losses were estimated to have been 1356 g·ha?1·y?1, 11.5 g·ha?1·y?1, 1436 g·ha?1·y?1, and 44 g·ha?1·y?1 respectively. Phosphorus and nitrate concentrations were similar in the Exotic Forest and Native Forest 2 streams, but the Exotic Forest tended to lose smaller amounts because it yielded about 50% less water per unit area.

Over the 2‐y study, an estimated 47–70% of phosphorus losses and up to 83% nitrate losses occurred in large floods; 31% and 48% respectively were apparently lost from the hill pasture catchment in a single flood. Less than 20% of estimated phosphorus losses and as little as 1% of nitrate losses occurred at low flows.

Run‐off of phosphorus and nitrate was spasmodic, and this should be considered in assessing the impact of surface run‐off on the biology and chemistry of receiving waters.  相似文献   

5.
Stream channels are narrower in pasture than in forest   总被引：1，自引：0，他引：1  
In the Hakarimata Range, west of Hamilton, New Zealand, second‐order streams appear to be wider in native than in pasture catchments, whereas streams in pine plantations (18 years old) appear to be suffering active stream‐bank erosion. A working hypothesis to explain these observations was that pasture vegetation replacing original forest encroaches on the stream channel, causing it to become narrower. To test the hypothesis, channel widths were measured up stream and down stream of “transitions” from native forest to pasture in 20 streams of different size in marginal ranges of the Waikato Basin. Small streams (catchment area <1 km2, width in forest <2 m) were found to be half the width in pasture reaches as in forest. The degree of channel narrowing decreased as stream size increased and was minimal in large streams (catchment area >30 km2, width in forest >10 m). This narrowing of stream channels implies that native forest clearance in New Zealand has reduced stream channel habitat. A concern regarding riparian planting for stream restoration is that sediment stored in pasture stream banks could be mobilised if grasses are extinguished by shading, resulting in turbid streamwater and sedimentation of fines in the channel.  相似文献   

6.
Water samples taken at 19 locations in the Mawheraiti River catchment at weekly intervals during 1979–80 were analysed for sodium, magnesium, potassium, calcium, phosphate, nitrate, and ammonium ion concentrations and for electrical conductivity. Seasonal discharge effects were apparent, and lithology and land management practice also influenced solute concentrations. Solute concentrations were generally very low; nitrate and soluble phosphate were rarely greater than 0.05 mg.L‐1 and ammonium was rarely greater than 0.01 mg.L‐1. The 4 major cations (Na, Mg, K, and Ca) usually summed to less than 6 mg.L‐1 much of which was supplied by precipitation. Forest management (clearfelling and slash‐burning) caused significant increases in solute concentrations, but concentrations declined rapidly during succeeding months and approached pretreatment levels after 2–3 years. The higher concentrations associated with forest management in small experimental catchments were rapidly diluted downstream; together with the low natural solute concentrations this suggests that harmful downstream effects of management practices are unlikely under low flow conditions.  相似文献   

7.
Two-year-old New Zealand geoducks (Panopea zelandica) were conditioned within combinations of three water temperatures (7–8, 11–12 and 16–17 °C) and three feeding rations (10,000, 50,000 and 100,000 cells mL?1 of Chaetoceros mulleri and Isochrysis galbana) for 73 days. Similar percent matured and dry condition index values were observed among temperatures. However, significantly higher dry gonadosomatic indices (GSIdw) were recorded at 8 and 12 °C. Although no difference was detected in percentage of spawned individuals and connective tissue occupation indices, a higher percent matured were recorded when fed 10,000 and 50,000 cells mL?1. A reference group conditioned in pond water became matured 2 months later than the other nine experimental groups, but GSIdw were similar. To maximise reproductive output, we suggest that 2-year-old P. zelandica may be conditioned in pond water for a month and then in 8 or 12 °C seawater with 50,000 cells mL?1.  相似文献   

8.
Abstract

The Whangamaire Stream (North Island, New Zealand) has high concentrations of nitrate nitrogen (NO? 3‐N), biochemical oxygen demand (BOD5), and Kjeldahl nitrogen (TKN) as a result of catchment land use practices. The lower reaches of the stream drain intensively farmed land and have dissolved oxygen (DO) levels of 10–50% saturation. The dominant riparian vegetation, Apium nodiflorum, provides a large organic loading by intercepting nutrients in run‐off and then decaying in the stream channel. Water quality and reaeration aspects of the stream were studied in order to explain the observed low DO levels. Measurements of the reaeration coefficient at 20°C, K2 20, using methyl chloride (CH3Cl) as a gas tracer, yielded values of 1.1–3.0 d?1 for the upper part of the study reach and 15.5–16.2 d?1 for the lower reach (overall average 12.5 ± 2.5 d?1). These were in agreement with values inferred from single‐station diurnal curve analysis, which also showed that respiration was dominant in the lower reach where photo‐synthetic activity was inhibited by shade. The relatively large reaeration coefficients ensure that parts of the stream do not become anoxic at night time. Better riparian management and reduced nutrient inputs are likely to improve stream water quality.  相似文献   

9.
Using data from existing studies, assemblages of freshwater fishes and decapod crustaceans were examined at 39 sites in urbanised catchments and 57 sites in forested (reference) catchments within the greater Auckland region, New Zealand. Eleven native and 1 exotic fish species and 2 native decapod crustacean species were recorded. Species richness and fish Index of Biotic Integrity (IBI) scores were lower overall in streams in urbanised catchments. Shortfin eel (Anguilla australis) and mosquitofish (Gambusia affinis) were more dominant in urban streams; all other commonly occurring species were found significantly more often in reference streams. Non‐diadromous native species (Cran's bully (Gobiomorphus basalts) and freshwater crayfish (Paranephrops planifions)) were absent from urban streams, but relatively abundant in reference streams. This absence of non‐diadromous species, together with the urban occurrence of five diadromous species suggests that migratory barriers pose less of a threat to freshwater communities than physico‐chemical disturbance in streams in the Auckland urban region.  相似文献   

10.
A total of 6085 adult Trichoptera (excluding Hydroptilidae) representing 12 families, 31 genera, and 56 species were collected by a combination of Malaise net and light trapping from July 1998 to July 1999 at three hill‐country sites of contrasting catchment land use (100% native forest, a pasture site with native forest headwaters, and 100% pasture) in the Waikato, northern New Zealand. Forty‐eight species of Trichoptera were collected from Malaise nets and 45 species from light traps. Eleven species of Trichoptera were only ever collected from the Malaise nets and seven species from only the light traps. At the native forest site, Malaise nets collected more species and taxa of conservation interest than did light traps, possibly reflecting diurnal activity or non‐attraction to light by some species. Several species of Trichoptera showed site specificity and most of these were found at the native forest site. Twenty‐eight species were active for at least 6 months of the year with at least four species active all year. A minimum overnight air temperature of at least 9°C was required to induce Trichoptera flight activity, but large‐scale flight activity may require temperatures greater than 14°C. Trichoptera with free‐living and net spinning larvae exhibited extended flight periods, and for three species examined there were bi‐modal activity peaks. Adult caddisflies with cased larvae which grazed on epilithic food resources generally had reduced flight periods and one species had a well‐defined, synchronous periodicity. These findings suggest flight periodicity may partly be a functional response to larval food availability.  相似文献   

11.
The ocean temperature field off the north‐east coast of New Zealand is studied to quantify the annual cycle and reveal the intra‐ and inter‐annual variability. The data used are repeat expendable bathythermograph (XBT) sections between Auckland and either Suva or Honolulu which have been collected quarterly since 1986. These sections give temperature measurements between the surface and 800 m and Auckland and 30°S from 1986 to August 1999. The mean and annual cycle are compared with those from the NOAA World Ocean Atlas (WOA98). The results are similar; however WOA98 lacks the horizontal resolution to fully discern the East Auckland Current and North Cape Eddy, while the XBT analysis lacks the temporal resolution to discern higher frequency intra‐annual signals. The temperature variability in the mixed layer is dominated by the annual cycle, which accounts for 80–90% of the variance. The amplitude of the annual cycle diminishes rapidly with depth, from 2.8°C at the surface, to c. 0.1°C at 180 m. The phase of the annual cycle is retarded with depth, with peak temperatures occurring in February at the surface and in June/July at 180 m. Removing the annual cycle from the time series reveals the more subtle inter‐ and intra‐annual variability. This variability is of the order of 1°C in the upper 50 m, decreasing to 0.3°C at 400–500 m. The surface layer was cold between 1991 and 1994 (c. 0.7°C cooler than average), and 0.7°C warmer than average in 1999. The deeper ocean shows a different signal, being up to 0.3°C cooler in 1990–92, 0.3°C warmer in 1998, and c. 0.2°C warmer than average in 1999. The inter‐annual mixed layer variability is highly correlated with the Southern Oscillation Index and also with inter‐annual terrestrial air temperature and wind measurements from northern New Zealand. In contrast, at higher intra‐annual frequencies, the mixed layer variability is not correlated with air and wind measurements. At these higher frequencies, the air temperature is better correlated with the sea surface temperature (SST) than with the bulk mixed layer temperature.  相似文献   

12.
于2009年6-9月在浙江省宁海县三门湾海域养殖场,选取2口水文环境相似的梭子蟹Portunus trituberculatus养殖池塘,分别采用“底充式增氧”(实验塘)和传统水车式增氧(对照塘)方式,比较研究了池塘水质环境及其浮游植物群落结构的变化.结果显示:(1)实验塘水质的溶解氧和氨氮指标均优于对照塘,其中实验塘...  相似文献   

13.
Water quality, habitat, and biota were compared during spring amongst c. 100 m reaches on 11 streams draining pasture, native (podocarp‐broadleaf) forest, and exotic pine forest established on pasture 15 years previously. Differences were greatest between the pasture and native forest streams. Only 1–3% of incident light reached native and pine forest streams whereas 30% reached pasture streams. Pasture streams had 2.2°C higher mean temperature than the native streams, and 5‐fold higher nitrate, 30‐fold higher algal biomass, and 11‐fold higher gross photosynthesis. Native streams were 60% wider than pasture, with pine streams intermediate. Pine and pasture streams had 3‐fold higher suspended solids and fine sediment stored in the streambed than native streams. Woody debris volume was 17‐fold greater in pine than pasture streams, with native streams intermediate. Invertebrate taxa richness did not differ between land uses. Community composition differed most between pasture and native forest, with pine forest streams intermediate. Invertebrate densities were 3‐fold higher in pasture than native streams, mainly because of more chironomids and snails, but mayflies, stoneflies, and caddisflies densities were 2–3‐fold higher in forest streams than pasture.  相似文献   

14.
Abstract

The density and biomass of fish and crayfish, and the production of eels, was compared among streams in native forest, exotic forest, and pasture. Populations were estimated by multiple‐pass electroshocking at 11 sites in hill‐country streams in the Waikato region, North Island. Three sites were in native forest, four in exotic forest, and four in pasture. Length of stream sampled at each site was 46–94 m (41–246 m2 in area), and catchment areas up stream of the sites ranged from 0.44 to 2.01 km2.

A total of 487 fish were caught. The species were longfinned and shortfinned eels, banded kokopu, Cran's and redfinned bullies, and common smelt. Eels were the most abundant fish in all three land‐use types, and shortfinned eels were more abundant at pastoral sites (mean density 1.11 fish m?2) than longfinned eels (mean density 0.129 fish m?2). Banded kokopu were present only at forested sites. Mean fish densities were greater at pastoral sites (1.55 fish m?2) than under either native forest (0.130 fish m?2) or exotic forest (0.229 fish m?2). Mean fish biomass was also greater at pastoral sites (89.7 g m?2) than under native forest (12.8 g m?2) or exotic forest (19.3 g m?2). Longfinned eels made a greater contribution to the fish biomass at all sites than did shortfinned eels. Densities of crayfish were high (0.46–5.40 crayfish m?2), but were not significantly different between land‐use types. Crayfish biomass ranged from 1.79 to 11.2 g m?2. Total eel production was greater at pastoral sites (mean 17.9 g m?2 year1) than at forest sites (mean 2.39 gm?2 year?1).  相似文献   

15.
Abstract

Nitrate runoff from pastoral fanning is of concern because it contributes to lake eutrophication. Surface flow in wetlands is a measure of the runoff likely to experience nitrate attenuation. This study assessed the potential of small headwater wetlands to reduce catchment nitrate loads by quantifying the proportion of total runoff that occurred as surface flow at the outlet of wetlands. Surface flow can be measured from wetlands in side valleys (valley wetlands) with well defined flow channels, but not in those parallel to the stream (riparian wetlands) with distributed flow. This study, from November 2004 to June 2008: (1) measured the mean specific flow yield (mm yr?1) at the outlet of 6 wetlands; (2) classified wetlands into 3 types based on hydrology; (3) mapped and classified all wetlands in the catchment; and (4) calculated the area‐weighted mean specific yield of wetlands for the whole catchment. The 6.6 km2 study catchment at Taupo, North Island, New Zealand, was predominantly pasture on volcanic soils where flows were baseflow dominated. Riparian and valley wetlands occupied 5% of catchment area. Type 1 wetlands flowed continuously, were dominated by baseflow (81–83%), and had a mean annual yield (± SE) of 167 ± 46 mm (34% of stream yield). Type 2 wetlands dried up during droughts and type 3 wetlands dried up each summer. Both latter types had a low baseflow component (20%) and a yield of 66±18 mm (13% of stream yield). In one tributary, gaugings over 4 days in summer during a wet year indicated that 27% of streamflow originated from wetlands. For the catchment as a whole, wetland baseflow accounted for 11± 4% of mean annual streamflow and wetland quickflow another 8 ± 2%, although these percentages are likely underestimates because seepages occurred downslope from measurement points. Although riparian and valley wetlands occupied only 5% of the catchment area, they could potentially have attenuated nitrogen in 11–19% of runoff. Other catchments may have different hydrology and wetland nitrate attenuation, and the methods outlined here could be used to quantify these differences.  相似文献   

16.
OVERSEER is used in New Zealand to estimate nutrient losses from farmland, but does not quantify subsequent movement through the catchment, or attenuation. This paper uses the ROTAN model, based on the Scandinavian HBV-N model, to route nitrogen losses from 1900–2015 to Lake Rotorua where groundwater age ranges from 14 to 170 years. ROTAN conceptualises three delivery pathways (quickflow, groundwater and streamflow) with different attenuation. When calibrated to measured stream and groundwater concentrations, several combinations of attenuation gave equally good fits largely because of sparse and uncertain input and calibration data. Nevertheless, lake N loads were predicted for current land use (754?±?39?t y?1) and with proposed N loss reductions (431?±?26?t y?1). Probabilities were also calculated that the reductions are more (12%–18%) or less (82%–88%) than required to meet the target lake N load (405?t y?1). ROTAN shows promise for calculating nitrogen movement in catchments dominated by groundwater where there is limited data.  相似文献   

17.
The Arabian Sea is characterized by a mid‐depth layer of reduced dissolved oxygen (DO) concentration or oxygen minimum zone (OMZ ‐DO concentration <0.5 ml·l?1) at ~150–1000 m depth. This OMZ results from the flux of labile organic matter coupled with limited intermediate depth water ventilation. Generally, benthic animals in the OMZ have morphological and physiological adaptations that maximize oxygen uptake in the limited oxygen availability. Characteristics of OMZ benthos have been described from only a few localities in the Arabian Sea. We measured the bottom water DO and studied the characteristics of infaunal macrobenthos of the Indian western continental shelf by collecting samples at 50, 100 and 200 m in depth from 7° to 22° N. The DO values observed at 200 m (0.0005–0.24 ml·l?1) indicated that this area is lying within an OMZ. Five major taxa, namely Platyhelminthes, Sipunculoidea, Echiuroidea, Echinodermata and Cephalochordata were absent from the samples collected from this OMZ. In general, declines in total macrobenthic density and biomass and polychaete species richness and diversity were observed in this OMZ compared with the shallower depths above it. Community analyses of polychaetes revealed the dominance of species belonging to families Spionidae, Cirratulidae and Paraonidae in this OMZ. Low oxygen condition was more pronounced in the northern continental shelf edge (≤0.03 ml·l?1), where the majority of spionids including Prionospio pinnata and cirratulids were absent; whereas amphipod, isopod and bivalve communities were not impacted.  相似文献   

18.
In this study, we explored the interactive effects of temperature and solar ultraviolet radiation (UVR) on the growth, pigment contents, photochemical efficiency and non-photochemical quenching (NPQ) of Pseudo-nitzschia pungens, which forms harmful algal blooms globally. Cells were first pre-acclimated to temperatures of 20°C, 25°C or 28°C for 10 days. They were then exposed to three different types of solar radiation for 60?min. We then measured the photochemical efficiency of the cells during the 60-min exposure and a 360-min recovery period under dim light (20?μmol?photons?m?2?s?1). In addition, we analysed the diural change in photochemical efficiency and NPQ over a 10-h period. We found that P. pungens that were exposed to higher temperatures in the short term (i.e. 20–25°C, 20–28°C and 25–28°C) or long term (i.e. 25–25°C and 28–28°C) exhibited lower levels of photoinhibition and faster recovery rates than samples exposed to a lower temperature (i.e. 20–20°C). This indicated that the deleterious effects of UVR can be minimised by both chronic and acute exposure to higher temperatures within the tolerated temperature range for P. pungens.  相似文献   

19.
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  
杜宝汉 《海洋与湖沼》1994,25(3):312-318
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   

20.
Conditions in artisanal salterns, or salinas, vary depending on their physical structure, seasonal effects, and the two periods of the salt production cycle. They therefore constitute unique wetland habitats, with particular communities that are still poorly studied. Water quality and zooplankton of a working artisanal salina were studied to evaluate spatial variability between sections and temporal variability between the salt production and flooded periods and between seasons. Zooplankton communities were related to environmental conditions. Sampling took place every second week, during almost two years, at six sites of the Tanoerias salina in Aveiro, Portugal: at the beginning and centre of the salina inlet channel, in a supply pond, in two evaporator and one crystalliser ponds. Since salt production occurs in the warm season only, seasonal effects concur with those caused by the salt production cycle. Results showed significant differences in temperature, dissolved oxygen (DO) and biochemical oxygen demand (BOD5) between salt production and flooded periods, i.e. summer and spring/winter seasons. Salinity and alkalinity were linked to salt production with extreme values in the salt-producing crystalliser pond. Zooplankton communities varied between seasons, but also with the salina section and the salt production cycle. Zooplankton densities and diversity tended to be lower during salt production, particularly under the extreme living conditions in the salina crystalliser pond. Variation in zooplankton communities between samples was mainly influenced by temperature, i.e. season, at the salina inlet, by BOD5 or DO, also related to temperature and season, in the first ponds and by nutrients throughout the system.  相似文献   

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