Seasonal succession and vertical distribution of phytoplankton in Lake Hayes and Lake Johnson,South Island,New Zealand

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.     

Response of zooid size in Cupuladria exfragminis (Bryozoa) to simulated upwelling temperatures

We investigate the effect of the temperature–size rule upon zooids of the tropical American bryozoan Cupuladria exfragminis. Results show that mean zooid length, zooid width and zooid area vary significantly between clonal replicates of C. exfragminis kept under different controlled temperature conditions. Significantly larger zooids are produced during times of lowered water temperature that are comparable with the temperatures that occur during seasonal upwelling along the Pacific coast of Panama where the animal lives in abundance. Interpolation of data suggests that a drop of 1 °C causes a 5% increase in zooid size, and that almost all variation in zooid size in natural populations can be explained by temperature. Results are discussed in context of the potential use of zooid size variation in cupuladriid bryozoans to measure the strength of seasonal upwelling in ancient seas by analysing zooid size changes in fossil colonies. The technique of cloning cupuladriid colonies by fragmentation is also discussed with reference to its benefits in experimental studies where genotypes need to be controlled or replicated.     

Effects of the toxic dinoflagellate Alexandrium tamarense on the greenshell mussel Perna canaliculus

Abstract

Oxygen consumption, grazing rate, and byssus production of the greenshell mussel Perna canaliculus were measured following exposure to bloom concentrations (10⁶ cells l^?1 ) of a toxic clone of the dinoflagellate AIexandrium tamarense (GT429), using anon‐toxic clone of the same species (PLY173) as control. Following feeding for 1 h on GT429, mussels (dry weight 54–127 mg) showed significantly increased oxygen uptake at 15°C (0.08 μl O₂ (mg dry tissue weight)^?1 ) compared with control mussels. However, following 24 h recovery, oxygen uptake was similar to initial values in all experimental conditions. The grazing rate of P. canaliculus fed upon toxic clone GT429 was 4.58 ± 0.76 cells mg^?1 h^?1 compared with 1.99 ± 0.47 cells mg^?1 h^?1 for PLY173. On exposure to A. tamarense, mussels maintained normal opening behaviour and there was no change in the byssus production over 24 h. It was concluded that P. canaliculus showed no dramatic physiological effects following short‐term feeding on the toxic strain of A. tamarense. During 2 weeks’ exposure to twice daily bloom concentrations of GT429, there was no mussel mortality. Toxicity in the tissues was 1295 μg STX equivalent per 100 g tissue, levels at which these mussels would be unsuitable for human or animal consumption.     

Notes on fecundity in the Marine spiny lobster Jasus edwardsii (Hutton) (Crustacea: Decapoda: Palinuridae)

Fecundity in the New Zealand spiny lobster Jasus edwardsii (Hutton) has been investigated by a detailed examination of 14 selected females “in berry” (i.e. carrying external eggs), ranging in carapace lengths from 9.5 cm to 17.0 cm. The following data were obtained for each specimen: (a) the total weight of eggs carried, (b) the average number of eggs per 1 g sample, and (c) the total number of eggs carried.

A positive correlation was noted between the total weight of eggs carried and increase in carapace length. The total weight of eggs carried ranged from 26.9 g in a small specimen of 9.5 cm C.L., to 123.9 g in a large female of 16.0 cm C.L. No relation was found between the average number of eggs per 1 g sample and increase in carapace length. A low count of 3,541 eggs per 1 g sample was recorded, and a high count of 5,005 eggs. A direct relation was noted between the total number of eggs carried by J edwardsii and increase in carapace length. The number of eggs carried ranged from a low figure of about 124,278 in a small specimen of 9.5 cm C.L., to a high figure of about 538,242 in a large female of 17.0 cm C.L. The rate of increase in fecundity was found to be greater in smaller than in larger females of J. edwardsii     

Grazing effects by Nereis diversicolor on development and growth of green algal mats

Nereis diversicolor is generally considered to be a predator and deposit feeder, but have also been found to graze on benthic algae in shallow coastal areas. In this study we investigated the grazing effects on the development and growth of green algae, Ulva spp. Algal growth was studied in an experiment including two levels of sediment thickness; 100 mm sediment including macrofauna and 5 mm sediment without macrofauna, and three treatments of varying algal biomass; sediment with propagules, sediment with low algal biomass (120 g dry weight (dwt) m^− 2) and sediment with high algal biomass (240 g dwt m^− 2). In the 100 mm sediment, with a natural population of macrofauna, N. diversicolor was the dominating (60% of total biomass) species. After three weeks of experimentation the result showed that N. diversicolor was able to prevent initial algal growth, affect growth capacity and also partly reduce full-grown algal mats. The weight of N. diversicolor was significantly higher for polychaetes in treatments with algae added compared to non-algal treatments. There were also indications that a rich nutrient supply per algae biomass counteracted the grazing capacity of N. diversicolor.     

摄食水平对异育银鲫生长及能量收支的影响

于 1 995年 6月在中国科学院水生生物研究所关桥繁殖场采集异育银鲫自繁鱼种(体重为 1 .2 6± 0 .0 5g) ,采用生长实验的方法 ,在 30℃水温下 ,测定其从饥饿到饱食 6个摄食水平下的生长和能量收支。结果表明 ,随着摄食水平的增加 ,鱼体干物质和能量含量、表观消化率呈上升趋势 ;湿重特定生长率随摄食水平的增加呈线性上升 ,干重和能量特定生长率呈对数增加 ;饲料转化效率随摄食水平增加而增加 ,达到最大值后维持不变。排泄能和总代谢耗能占摄入食物能的比例不受摄食水平的影响。最大摄食水平下的能量收支式为 :1 0 0C =1 2 .32F 3.2 1U 63.74R 2 0 .72G ,式中 ,C为食物能 ,F为粪便能 ,U为排泄能 ,R为代谢能 ,G为生长能。     

稀土对球等鞭金藻生长的影响

于１９９５年８－１２月,利用单因子实验法,首次研究了混合稀土对球等鞭金藻（Ｉｓｏｃｈｒｙｓｉｓｇａｌｂａｎａ）生长繁殖的影响,结果表明,海水中稀土最佳浓度范围为１．６６－６．６０ｍｇ／Ｌ,细胞浓度和叶绿素含量分别提高１１．６％－２３．２％和１９．９％－４５．２％混合稀土加入浓度高于９．９ｍｇ／Ｌ对球等鞭金藻的生产产生抑制作用,稀土对球等鞭金藻生长的促进作用与其他营养盐类浓度有关,当细胞处于指数生长     

Diversity and Distribution of the Bryozoa along Underwater Cliffs in the Adriatic Sea with Special Reference to Thermal Regime

Abstract.  The diversity and distribution of bryozoans have been surveyed at two localities, Cape Struga on Lastovo Island (South Adriatic) and Cape Šilo on Prvić Island near Senj (North Adriatic), with similar characteristics of topography and exposure but markedly different sea temperature conditions. Continuous measurements over one year have shown that temperature conditions differ in two aspects. First, the annual range of temperature is much larger in the North. Second, in the South during summer, marine life within the thermocline layer is exposed to large high-frequency temperature oscillations, partly due to an internal diurnal tide, a phenomenon recorded for the first time in the Adriatic. Altogether, 78 species have been recorded, 57 in Lastovo and 50 in Prvić, and 29 in both localities. The comparison of mean zooid lengths of 14 bryozoan species occurring at both localities indicates no consistent difference in zooid size between northern and southern sites. Seventeen bryozoan species have been recorded in the Eastern Adriatic Sea for the first time.     

Growth and Production in Posidonia Oceanica (L.) Delile*

Abstract. In situ investigations of growth and production in a stand of Posidonia oceanica (L.) DELILE at a depth of 4 m at Ischia (Gulf of Naples) were carried out over two growing seasons. Posidonia starts to grow in August and an average bundle produces ten leaves in increasing time intervals until May. Growth curves for the leaves are given. Maximum leaf standing crop is in May with 1300 g dry weight per m^-2, leaf area index at this time reaches 22 m² m^-2. Leaf net productivity is highest in March with 12 g dry weight per m² per day. Annual leaf production is estimated as 3110 g dry weight per m², “underground” production as 115 g dry weight per m². About half the leaf production is exported from the system. Adaptive strategies of the growth and production pattern are discussed.     

南方鲇的排粪量及消化率同日粮水平、体重和温度的关系

于１９８８年２月－１９８９年２月测定了南方鲇幼鱼的排粪量，从而估算共消化率。结果表明，当水温为２５℃时，在日粮水平分别是体重的１％，２％，４％和达饱食的条件下，平均消化率分别为摄入食物能量的８０．３２％，８４．９４％，８８．４０％ｔ ８７．２７％；在平均初始体重分别为８．７２，２５．４３，４５．１６，７８．１８和１２７．５ｇ的实验组中，平均消化率分别为８６．５９％，８１．１５％，９０．３８％，８６     

Stable isotope composition of modern bryozoan skeletal carbonate from the Otago Shelf,New Zealand

The oxygen (δ¹⁸O) and carbon (δ¹³C) isotope ratios of 10 species of living Bryozoa collected from the Otago Shelf, New Zealand were analysed to assess the extent to which isotopic equilibrium (relative to inorganic equilibrium isotope fractionation) is attained during the precipitation of skeletal calcium carbonate. The data reveal that whereas eight species of Bryozoa synthesise skeletal carbonate in apparent oxygen isotope equilibrium with respect to environmental conditions, two species (Celleporina grandis and Hippomonavella flexuosa) yield δ¹⁸O_calcite values which indicate significant disequilibrium oxygen isotope fractionation during calcification. Sufficient data are available from one species (C. grandis) to demonstrate that disequilibrium is probably related to kinetic factors associated with diffusion‐controlled transport of HCO₃‐ to the site of calcite precipitation. Carbon isotope signatures indicate significant departures from inorganic isotope equilibrium in all but one bryozoan species (Hippomenella vellicata). Although greater uncertainties are associated with estimates of the isotopic composition of total dissolved inorganic carbon (δ¹³C_SDIC), the data suggest that two factors—kinetic fractionation and incorporation of respiratory CO₂—are important in controlling carbon isotope disequilibrium. Where bryozoan species exhibit evidence for disequilibrium in both oxygen and carbon isotope systems (C. grandis, H. flexuosa), it is likely that kinetic factors are primarily responsible for observed departures from carbon isotope equilibrium. In contrast, the probable explanation for those species which display evidence for carbon isotope disequilibrium only, is that skeletal carbonate is precipitated from a DIC pool modified by the incorporation of respiratory CO₂. Differences between the carbon isotope composition of skeletal elements from the same species and co‐existing species living in the same community suggests that significant variations may occur in the extent to which marine DIC and respiratory CO₂ are utilised during calcification. Additional studies of carbon pathways associated with calcification are required to assess the relative effects of kinetic, metabolic, and environmental factors on the carbon isotopic composition of bryozoan skeletal carbonate.     

Effects of destroying juxtaposed mussel-dominated and coralline algal communities at Umdoni Park,Natal coast,South Africa

An experiment was conducted to determine the recruitment pattern of species into disturbed areas of the lower littoral zone. Plots were cleared to rock substratum in two juxtaposing communities, one dominated by the mussel Perna perna (Linn.) and the other by foliose and crustose coralline algae (Rhodophyceae). Subsequent changes in cover were monitored for one year. Undisturbed sectors of these two communities were also monitored for comparative purposes. Evaluations were made by comparing species similarity indices and biomass measures. Within five months all cleared plots had recruited a richer species composition and a biomass comparable to that of an undisturbed community dominated by coralline algae. The mussel Perna perna, during the experiment and up to eight years later, never returned to numerical dominance in the experimental plots. The consequences of this for the welfare of mussel beds are discussed.     

Variation in sunscreen compounds (mycosporine‐like amino acids) for marine species along a gradient of ultraviolet radiation transmission within doubtful sound,New Zealand

We examined the response of four species of New Zealand marine algae (Ecklonia radiata, Apophlaea lyallii, Rhodymenia spp., Ulva lactuca) and a sea urchin (Evechinus chloroticus) to spatial variation in ultraviolet radiation (UV‐R) by examining the concentration of UV‐R absorbing compounds known as mycosporine‐like amino acids (MAAs). The purpose was to understand how, and the degree to which, local marine species could potentially respond to any future increases in incident UV‐R in the New Zealand marine environment. The research was undertaken in Doubtful Sound, where we observed a gradient of water column UV‐R transmission along the 40 km length of the fiord. We examined spatial differences in MAAs along the UV‐B gradient in the macrophytes and temporal changes in MAAs in sea urchin gonads. Among the algae, thallus MAA concentrations (nmol mg^–1 protein) ranged from 12.5 to 87.8 in E. radiata, from 433.1 to 1446.4 in A. lyallii, 12.7 to 103.4 in Rhodymenia spp., but were not detected in U. lactuca. For E. chloroticus, gonadal MAA concentrations ranged from 83.9 to 224.3 nmol mg^–1 protein spatially, and over the year from 1.85 to 14.12 nmol mg^–1 dry weight (DW) depending on site and gametogenic cycle. Laboratory manipulations indicated that concentrations of MAAs in E. chloroticus gonads and eggs are influenced by diet. MAA concentration could be correlated with UV‐B intensities in two of the algal species. E. chloroticus MAA concentrations could also be correlated with UV‐B transmission, which we concluded was a reflection of the greater ingestion and accumulation of MAA‐rich macrophytes at those sites where higher ambient UV‐R induced greater MAA concentrations to occur in the algae. Given this, we suggest that one response of marine species to increases in UV‐B would be an increase in the synthesis and/or accumulation of MAAs for photoautotrophs and a dietary accumulation of those MAAs in E. chloroticus, an important herbivore in this system.     

Colony formation in the Cheilostomatous Bryozoan Fenestrulina Malusii var. Thykeophora

The early stages of colony formation of Fenestrulina malusii var. thyreophora are described, and notes on two other species are included for comparison. In Fenestrulina, early budding patterns are very variable, although some patterns are commoner than others. At the 3‐zooid stage of colony formation there is usually temporary suppression of budding on one side, with the result that the three first‐generation zooids produced from the ancestrula arise 1, 2, 4 in the commonest budding sequence rather than 1, 2, 3; budding patterns may be considerably modified when colonies are obstructed. In Fenestrulina and Eurystomella foraminigera the first zooid budded from the ancestrula lies in the distal midline whereas the second zooid occupies this position in Crassimarginatella papulifera. In all three species the proximal periancestrular zooids are not budded directly from the ancestrula but belong to the third zooidal generation.     

Ecological and physiological features of the mesopelagic mysid,Meterythrops microphthalma,in the Japan Sea

The abundance and vertical distribution pattern of a mysidMeterythrops microphthalma were investigated in the Japan Sea. Results from vertical hauls from 602–982 m depth to the surface around Yamato Rise in April 1987 indicated that the dominance (by biomass) ofM. microphthalma was third to fifth of major zooplankton taxa. Vertical distribution investigated at a single station in Toyama Bay in June, September and December 1986 showed that the most part of population of this mysid inhabited consistently below 250 m depth. No marked diurnal vertical migration was evident. Data on body composition and oxygen consumption rate ofM. microphthalma are presented. Water content of the body was 75.6–83.8% of wet weight, and ash was 11.4–20.4% of dry weight. Carbon, hydrogen and nitrogen were 37.9–47.5%, 6.2–7.4% and 9.4–10.1%, respectively, of dry weight. Oxygen consumption rates were 2.2–11.0µl O₂ individual^–1 hr^–1 at 0.5°C, and were directly proportional to body mass. From the comparison with the published data on epipelagic and bathypelagic mysids it is revealed that both body nitrogen composition and oxygen consumption rate expressed as adjusted metabolic rate [AMR₀₂,µl O₂ (mg body N)^–0.85 hr^–1] ofM. microphthalma are intermediate between high epipelagic and low bathypelagic levels, indicating typical mesopelagic features.     

光周期对罗氏沼虾幼体生长及能量收支的影响

于１９９５年２－５月,在Ｌ：Ｄ为４：２０,８：１６,１２：１２和２４：０四种光周期条件下,用卤虫无节幼体作饵料增减罗氏沼虾幼体,测定其生长能量收支。结果表明,随着光照时间的延长幼体生长率增大,两者关系为：ｇ＝６．５２４５＋３．６０４５ｌｎＴ,但周期对幼体Ｃ,Ｎ含量和Ｃ：Ｎ值没有显著的影响;     

Expected changes in the benthic fauna of Wadden Sea tidal flats as a result of sea-level rise or bottom subsidence

In different parts of the Dutch Wadden Sea, relationships between intertidal level and abundance of marine macrozoobenthos were similar. Numerical densities, biomass and species richness increased from values close to 0 at the high-water level to maximum values around mean-tide level (numbers) or halfway between this level and low-tide level (biomass). Species richness hardly declined below mean-tide level, whereas mean weight per individual continued to increase from high- to low-water level.Biomass was about 45 g ash-free dry weight per m² at its maximum and declined in an approximately linear way to values close to 0 at the high-water level and to about 7 g per m² at the low-water level. These two linear relationships were used to predict biomass changes on intertidal flats of the Wadden Sea at various scenarios of sea-level rise and bottom subsidence. Net sea-level rise is expected to result in increased amounts of intertidal zoobenthos in areas with predominantly high tidal flats, but in declines in lower areas. However, such changes will occur only if sea-level rise proceeds too fast to be compensated by extra sedimentation. Bottom subsidence as a consequence of gas extraction is expected to be too small to cause any measurable change in the benthic fauna.     

Bacterial populations,heterotrophic potentials,and water quality in three New Zealand Rivers

Abstract

Thirty sites were sampled in three New Zealand rivers (Waikato, Maitai, and Wakapuaka) during late summer 1977. Samples were collected from just below the surface at mid river or in the tailraces below hydro‐electric dams.

Parameters measured included bacterial numbers (direct counts), heterotrophic potential (V_max ), adenosine triphosphate (ATP), chlorophyll a (Chi a), and concentrations of nitrogen and phosphorus compounds.

Bacterial populations per millilitre fluctuated threefold (6.4–19.4 × 10⁵) along the Waikato River and were lower and more consistent in the two South Island rivers (1.46–2.55 × 10⁵). In contrast, V_max varied 5000‐fold in the Waikato River, from a characteristically oligotrophic value of 0.0035 μg. l^?1·h^?1 (Lake Taupo outlet) to a eutrophic value of 18.4 μg. l^?1·h^?1 at the Mihi bridge. V_max for the two South Island rivers ranged from 0.0091 to 0.189 μg. l^?1 · h^?1.

ATP, Chi a, Kjeldahl nitrogen, nitrate nitrogen, and total phosphorus concentrations for the 20 sites on the Waikato River varied in a similar way to the V_max and bacterial data. There were large peaks at the Mihi bridge, lower values for the dam tailraces and significant increases for the sites below Hamilton. Concentrations for these parameters were lower and more consistent along the lengths of the two South Island rivers.

Most parameters were significantly correlated with each other for the Waikato River samples. The strongest correlations were between V_max and bacterial numbers and between V_max and nitrate nitrogen. In the Maitai and Wakapuaka River series these correlations were also significant, but the only other significant correlations recorded there were between ATP and nitrate nitrogen, and between ATP and bacterial numbers.     

Oxygen consumption in the epilimnia and hypolimnia of two eutrophic,warm‐monomictic lakes

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.     

Limnology of Lake Rotokawa and its outlet stream

Abstract

The water chemistry, flora, and fauna of Lake Rotokawa (38° 37.8’ S, 176° 11.2'E) was studied in 1975–76. The mean pH is 2.1 and thermal inflows may elevate the mean summer temperature of the surface waters 4.2°c above that of nearby cold water Lake Rotongaio (18.9°c). The temperature range of surface water was from 10.1 °c in winter to 23.1°c in summer. The major anions were SO₄ ^2? 679 g.m^?3, and Cl‐ 314 g.m^?3. Mean concentrations of major cations were Na⁺ 224 g.m^?3, K⁺ 28.9 g.m^?3, Ca²⁺ 13.3 g.m^?3, and Mg²⁺ 2.6 g.m^?3.

Two species of flagellate algae were recorded, of which Euglena anabaena was predominant. Only two benthic macroinvertebrates were found, larvae of Chironomus zealandicus, mean density 253 per square metre, and Helobdella sp., 1.3 per square metre.

The Parariki Stream was influenced by thermal springs in its upper and lower reaches, being cooler (24–25°c) about halfway along its length than near its source (27.8–39.0°c) or confluence (26.5°‐28.0°c) with the Waikato River. In the cooler stretch of the stream where unidentified benthic algae were not limited by high temperature, chlorophyll and total pigment increased from 3.9 to 377.9 mg.m^?3 and from 17.5 to 534.4 mg.m^?3 respectively, and nutrient levels fell (NO₃‐N, 22–10.5 mg.m^?3; NH₄‐N, 6440–230 mg.m^?3; and PO₄‐P, 51–19 mg.m^?3).