Immigration and settlement pattern of Paralichthys dentatus and P. lethostigma in an estuarine nursery ground,North Carolina,U.S.A.

Immigration and settlement pattern of 0-group summer flounder (Paralichthys dentatus) and southern flounder (P. lethostigma) in an estuarine nursery are described. Flounders entering the estuary were transforming larvae. Despite their sympatric occurrence during larval immigration, the two species were found concentrated in different habitats. Sampling along transects within the estuary indicated that newly settled southern flounder were concentrated on tidal flats towards the head of the estuary while greatest numbers of summer flounder were captured on tidal flats in the middle reach of the system. Logistic regression analysis of presence/absence data indicated that salinity affected the distribution of southern flounder while substrate type was an important factor affecting the distribution of summer flounder. Numbers of both species on tidal flats declined in the spring, southern flounder appeared to move upstream to oligohaline riverine habitat and summer flounder appeared to move to high salinity salt marsh habitat. The segregated distribution apparent in juveniles is largely established during the immigration period. Differences in settling behaviour and subsequent movement and/or differential mortality occurring during settlement, appear important in determining the observed distribution of juvenile summer and southern flounder.     

Daily fecundity of Temora longicornis (Copepoda calanoida) in the Oosterschelde estuary (SW Netherlands)

Daily fecundity of Temora longicornis in the Oosterschelde was estimated in 1986 and 1987 after 24 h incubation of female copepods collected in the estuary. Daily egg production fluctuated between 3 and 25 eggs per female.Egg production rates increased with temperature in the range of 3 to 15°C when algal food was present in excess. Limiting food conditions were found at the end of the phytoplankton spring bloom and occasionally in summer at concentrations of ⩽2 μg chlorophyll·dm⁻³. When chlorophyll maxima were found, predominantly consisting of Phaeocystis, daily fecundity of Temora was suppressed. It could increase, however, in Phaeocystis blooms mixed with diatoms (Rhizosolenia delicatula).Standing stocks of eggs in the springs of 1986 and 1987 were calculated on the basis of the established temperature/fecundity relation and compared with observed numbers, both in the years 1986 and 1987 (estuary provided with a storm-surge barrier in the mouth) and in the years 1983 and 1984 (open estuary).Smaller differences between observed and calculated egg numbers in 1986 and 1987 could be ascribed to possible errors in calculated egg development time and to the different age structure of females in the course of time.Much larger differences were found between the years 1986–1987 and 1983–1984. These are discussed in relation to the following phenomena: sinking of eggs, cannibalism, predation, food quantity and availability, density-dependent effects, hydrodynamical changes of the estuary. Arguments are given for density-dependent factors being responsible for the strongly reduced egg numbers in 1984.     

The distribution of suspended matter in the Dutch coastal zone

Results are presented of suspended matter observations taken at bi-weekly intervals during the period 1975–1983, in a strip 70 km wide along the Dutch coast. The average distribution showed a (weak) minimum zone located north of Noordwijk at a distance of about 30 km from and parallel to the Dutch coast, between the salinity maximum and the coast. Variability was large between different years, seasons and individual cruises. A clear seasonal cycle emerged from the observed suspended-matter patterns: in winter a pronounced minimum existed, while in summer generally a monotonically decreasing concentration was measured, to open-sea values much lower than in winter. This seasonal cycle may be explained by a combination of variation in wind, river discharge and the activity of suspended-matter sources. The Flemish Banks and Channel waters are the main sources supplying suspended matter to the Dutch coastal area. Especially the varying transport through the Strait of Dover, large in winter, small in summer, determines the seasonal variation in the total amount of suspended matter. The existence of a localized turbidity minimum is tied to relatively large discharges from the Rhine and associated steep salinity gradients, also occurring mainly in winter and early spring. A simple model of cross-shore density-driven circulation shows the possible influence of the strong salinity gradients on the sedimentation of suspended matter. Particles with a settling rate comparable to the vertical velocity component of the circulation are forced to move offshore until they reach an area they sink out of the surface layer. The strength of this circulation is determined by the cross-shore density gradient due to the inflow of fresh water from the Rhine-Meuse estuary.     

Dynamics of dissolved silicium and nitrogen-nutrients at low temperature in the Ems-dollard estuary

With salinity and natural fluorescence as conservative tracers to discriminate between fresh water contributions from two different fresh water sources (the river Ems and the river Westerwoldse Aa), deviations from conservative behaviour for silicate, ammonia and nitrate during winter conditions (4–6°C) are reported and discussed. For silicate a net removal from overlying water during transport through the estuary of 15% was found. Nitrification in overlying water (260 μmol·m⁻³·h⁻¹) was the only important process in nitrogen cycling; sediment-water exchange was of no importance during this period.     

The effect of deficit irrigation on crop yield and vegetative development of Olea europaea L. (cvs. Frantoio and Leccino)

Water is the most important environmental constrain determining plant growth and fruit yield of olive tree plantations. Although olive trees are resilient to water-limited conditions of Mediterranean-type agroecosystems, crop yields may respond positively to any additional water up to a limit. A field experiment on olive trees was carried out with the aim to present guidelines for efficient management of irrigation scheduling, based on the relationship between plant water status and optimum fruit yield. These relationships were monitored during 2 years by analysing the influence of deficit irrigation strategies on vegetative development and yield parameters on mature modern-trained olive trees of cvs. Frantoio and Leccino. Treatments were: a non-irrigated control (rainfed) and three treatments that received seasonal water amount equivalent to 33, 66 and 100% of ET_C in the period August–September, from the beginning of pit hardening to early fruit veraison. Atmospheric evaporative demand and soil moisture conditions were regularly monitored. Seasonal dynamics of plant water relations varied among treatments, and responded to variations in tree water status, soil moisture conditions and atmospheric evaporative demand. All measurements of tree water status were highly correlated with one another. Differences in yield between treatments indicated that water availability might have affected fruit weight before flowering or during the early stages of fruit growth rather than later in summer season. Results concerning crop yield revealed that irrigation of olive trees from the beginning of pit hardening could be recommended, at least in the experimental conditions of this study and in view of differences between genotypes.     

The effect of deficit irrigation on crop yield and vegetative development of Olea europaea L. (cvs. Frantoio and Leccino)

Water is the most important environmental constrain determining plant growth and fruit yield of olive tree plantations. Although olive trees are resilient to water-limited conditions of Mediterranean-type agroecosystems, crop yields may respond positively to any additional water up to a limit. A field experiment on olive trees was carried out with the aim to present guidelines for efficient management of irrigation scheduling, based on the relationship between plant water status and optimum fruit yield. These relationships were monitored during 2 years by analysing the influence of deficit irrigation strategies on vegetative development and yield parameters on mature modern-trained olive trees of cvs. Frantoio and Leccino. Treatments were: a non-irrigated control (rainfed) and three treatments that received seasonal water amount equivalent to 33, 66 and 100% of ET_C in the period August–September, from the beginning of pit hardening to early fruit veraison. Atmospheric evaporative demand and soil moisture conditions were regularly monitored. Seasonal dynamics of plant water relations varied among treatments, and responded to variations in tree water status, soil moisture conditions and atmospheric evaporative demand. All measurements of tree water status were highly correlated with one another. Differences in yield between treatments indicated that water availability might have affected fruit weight before flowering or during the early stages of fruit growth rather than later in summer season. Results concerning crop yield revealed that irrigation of olive trees from the beginning of pit hardening could be recommended, at least in the experimental conditions of this study and in view of differences between genotypes.     

短期NaCl与Na2CO3胁迫对紫花苜蓿种子萌发可恢复性的影响

探讨短期钠盐胁迫对紫花苜蓿种子萌发特性的影响。试验共设盐分类型、盐分浓度、温度及胁迫时间等4个因子,测定发芽率（势）等指标。结果表明：短期钠盐胁迫解除后,30℃发芽率最低,但温度无持续效应,前期温度仅影响前3天发芽,而不影响后期发芽;Na2CO3具有持久的抑制效应,各个测定指标均低于NaCl;随盐分浓度提高,发芽率逐渐降低,尽管250 mM显著抑制前3天发芽,但第5天该处理有显著恢复性萌发,表明盐分浓度为暂时性抑制效应;胁迫时间与盐分浓度效应类似,随胁迫时间延长,发芽率逐渐下降,30 h抑制前3天萌发,但胁迫解除后有较高的恢复萌发。     

Environmental Interactions between Different Tree Species and Mung Bean (Vigna radiata (L.) Wilczek) in Hedgerow Intercropping Systems in Sri Lanka

Annual crops grown in association with contour hedgerows often show yield reductions. This paper quantifies the variation of above- and below-ground environmental factors in hedgerow intercrops involving six different tree species ( Calliandra calothyrus , Desmodium ransonii , Flemingia c ongesta , Gliricidia sepium , Cassia spectabilis and Tithonia diversifolia ) and thereby shows the effects of tree hedges on mung bean ( Vigna radiata ). Compared to a sole crop of mung bean, most hedgerow intercrops removed greater soil nitrogen, whereas all removed lower soil phosphorus. Mung bean closer to the hedgerows had lower N and P, indicating competitive capture of nutrients by hedges. Most hedgerow intercrops had greater top-soil water because of their shading effect, especially near hedgerows. However, greater absorption by tree root systems decreased subsoil water near hedgerows late in the season. Soil temperature was lower in most hedgerow intercrops than in the control and increased with increasing distance from hedges. During initial stages of mung bean growth, radiation interception of intercrops was greater than that of the control, especially closer to hedgerows. However, after the first month, radiation interception of the sole crop was either equal to or greater than that of hedgerow intercrops. There was significant variation between tree species in all these environmental factors. Gliricidia , which allowed greater mung bean yields, also allowed greater nutrient capture by mung bean, greater top-soil water availability, lower extraction of subsoil water and lower soil temperatures.     

Primary production of phytoplankton in a turbid coastal plain estuary,the Westerschelde (The Netherlands)

An extensive survey was carried out in the Westerschelde estuary in 1989 to estimate phytoplankton primary productivity. High nutrient concentrations year round and very high turbidity resulted in light-limited growth of phytoplankton. This was reflected in a conservative behaviour of silicate and phosphate. The same was true for total inorganic nitrogen. However, in the inner part of the estuary nitrification took place. The calculated annual primary production was 200 – 300 gC·m⁻² at the range 29-20 salinity, 100–150 gC·m⁻² at 18-10 salinity and increased sharply to 900 gC·m⁻² at 2.5 salinity due to freshwater populations. In the inner part of the estuary the vertical mixing zone was frequently larger than 5 times the euphotic zone. The high rates of primary production we measured contrast with generally expected values. This corroborates Grobbelaar's hypothesis that the critical depth can be seriously underestimated. Phytoplankton copes with the turbid conditions by adjusting light-utilization efficiencies.     

Environmental characteristics and distribution of macrobenthos in a mudflat of the west coast of Korea (Yellow Sea)

The spatio-temporal changes of environmental factors and the distribution patterns of macrobenthos were investigated on an intertidal mudflat near Panweol on the west coast of Korea. Temperatures of the surface sediments and salinities of the intertitial water were highest in summer and lowest in winter, while water content of the sediment was lowest in summer and highest in winter. Hourly variations of sediment temperature, water content and interstitial salinity during the daytime depended largely upon both the timing of ebb tide and daylight intensity.Temperature, water content and interstitial salinity showed a marked variation with sediment depth. Temperatures decreased sharply from the surface to 10 or 15 cm depth, and below this depth they were nearly constant, except in summer. Water content and interstitial salinity underwent a rapid decline in this upper layer and began to rise from this depth. From the high tide mark toward the main tidal channel, water content increased but salinity decreased. The sand fraction increased with the decrease of clay content toward the main tidal channel. This tidal flat could be divided into two zones: the “upper intertidal zone” and the “lower intertidal zone”, based on the spatial differences of the water content, interstitial salinity and grain-size composition in the surface sediment.There were three distinct zones of macrobenthos. The upper intertidal zone was dominated by burrowing deposit feeders, such as Ilyoplax dentimerosa, Helice tridens sheni, Cleistostoma dilatatum and Perinereis vancaurica tetradentata. The middle intertidal zone was characterized by other burrowing deposit feeders, such as Ilyoplax pingi, Macrophthalmus japonicus and Periserrula leucophryna. And the lower intertidal zone was dominated by suspension feeders represented by Laonome tridentata and Potamocorbula amurensis. Each zone was named after these characteristic species.Although the species composition of the upper intertidal community was different from that of the middle intertidal, the way of living and the feeding behaviour of the species occurring in these two zones were very similar. But the lower intertidal zone showed a characteristic community structure differing not only in species composition but also in ways of living and feeding of the species. Some sets of environmental factors are considered to explain the zonation. Water content of the sediment and interstitial salinity will be the main factors causing the observed zonation.     

Flocculation and de-flocculation of suspended matter in estuaries

Flocculation and de-flocculation have been observed in estuaries and the processes involved are discussed. Salt flocculation plays a minor role, if any. Flocs are mainly formed by a combination of two groups of processes: those bringing particles together, and those keeping them together. The first group is related to the flow conditions in the water and to organisms that clog particles into faeces or pseudofaeces or attach them to mucus. The second is related to the formation of sticky organic matter by a variety of organisms. Two main types of flocs have been observed: microflocs with a diameter up to 125 μm, and macroflocs with a maximum size of 3–4 mm. Microflocs consist of mineral particles and organic matter. Their formation is strongly related to the origin of the organic matter, to the organisms producing it, and to conditions of (temporary) deposition and resuspension. Mucopolysaccharides, produced by bacteria, algae and higher plants and mobilized from the suspended matter at low salinity, are important in glueing particles together. The microflocs, together with single mineral particles, are the basic building units of macroflocs. Macroflocs are fragile and formed in the water under conditions of viscous flow. Their maximum size is determined by turbulent shear, the size of the smallest turbulent whirls on the Kolmogorov scale being of the same order as the maximum floc size. They are easily destroyed during sampling. In estuaries the microflocs of fluvial origin are broken up by organisms consuming the organic matter in the microflocs, and reflocculated into new microflocs with newly formed organic matter of estuarine origin. The size of the microflocs, as seen under a microscope or determined by size analysis, is likely to be determined mainly by the binding strength of the organic matter in relation to the total mass of the floc and the physical disturbance produced during sampling and size analysis.     

Breeding for yield, in mixtures of common beans (Phaseolus vulgaris L.) and maize (Zea mays L.)

Summary Despite the growing industrialization, technification and transformation that is happening in the agriculture around the world, and despite that agricultural research has always concentrated its effort on sole crops, multiple cropping systems have historically been important for common bean production in tropical countries. The reasons for this fact, are economical and social, as well as biological. Bean breeders have always been questioned on their work, because the development of new varieties is usually done in sole crop, but the varieties are grown in either systems. This paper addresses a set of questions that are usually presented to the breeders, in light of the evidence obtained from many trials conducted in Brazil and in the U.S.A.: Will the genotypes bred for sole crop conditions, perform well when grown in intercrop; How different should a genotype be, for cultivation in intercropping compared to genotypes developed for sole crop conditions; Is there a need for special breeding programs for intercropping and How could a breeding program focus the question of multiple (associated) cropping?     

Effects of Salinity and Soil–Drying on Radiation Use Efficiency,Water Productivity and Yield of Quinoa (Chenopodium quinoa Willd.)

Drought and salinity reduce crop productivity especially in arid and semi‐arid regions, and finding a crop which produces yield under these adverse conditions is therefore very important. Quinoa (Chenopodium quinoa Willd.) is such a crop. Hence, a study was conducted in field lysimeters to investigate the effect of salinity and soil–drying on radiation use efficiency, yield and water productivity of quinoa. Quinoa was exposed to five salinity levels (0, 10, 20, 30 and 40 dS m^?1) of irrigation water from flower initiation onwards. During the seed‐filling phase the five salinity levels were divided between two levels of irrigation, either full irrigation (FI; 95 % of field capacity) or non‐irrigated progressive drought (PD). The intercepted photosynthetically active radiation was hardly affected by salinity (8 % decrease at 40 dS m^?1) and did not differ significantly between FI and PD. Radiation use efficiency of dry matter was similar between salinity levels and between FI and PD. In line with this, no negative effect of severe salinity and soil–drying on total dry matter could be detected. Salinity levels between 20 and 40 dS m^?1 significantly reduced the seed yield by ca. 33 % compared with 0 dS m^?1 treatment owing to a 15–30 % reduction in seed number per m², whereas the seed yield of PD was 8 % less than FI. Consequently, nitrogen harvested in seed was decreased by salinity although the total N‐uptake was increased. Both salinity and drought increased the water productivity of dry matter. Increasing salinity from 20 to 40 dS m^?1 did not further decrease the seed number per m² and seed yield, which shows that quinoa (cv. Titicaca) acclimated to saline conditions when exposed to salinity levels between 20 and 40 dS m^?1.     

Suspended-sediment transport in the Dollard estuary

For an analysis of suspended-sediment transport in the Dollard estuary, water samples were taken and current velocities and directions measured on the tidal flats and in the channels. Measurements carried out during fair-weather conditions in summer were compared with measurements carried out during a heavy gale in winter. During the onset of the flood, high suspended-sediment concentrations occurred as a result of resuspension of the top layer of the bottom sediment. Measurements carried out in the channels pointed to sediment transport from the estuary seaward, but inward transport over the flats during fair weather apparently compensates for the outflow during ebb and storms: the result is a net deposition in the order of 1 to 2 mm (up to 8 mm) per year, as previously observed in this area.     

Seasonal Development of Genotypic Differences in Sugar Beet (Beta vulgaris L.) and Their Interaction with Water Supply

Depending on genotype, sugar beet can differ considerably in yield and quality characteristics. These are additionally modified by environmental conditions with drought stress recently gaining in importance, restricting growth and altering the chemical composition of the beet. The occurrence and development of these genotypic differences during the vegetation period and their possible interaction with environmental conditions were investigated. In 2002 and 2003, four sugar beet genotypes differing in yield and quality and putative different with regard to drought tolerance were tested in field trials, partly under irrigated conditions, in a total of 10 environments with consecutive harvests starting in early summer. In 2 years of stress and non-stress conditions they exhibited significant differences for taproot and leaf dry matter and the concentration of sucrose, K, Na and α-amino nitrogen in the taproot. These differences existed already in mid-June and virtually did not change any more from this time on. Accordingly, interactions between genotype and harvest date did not occur. For sugar beet, genotype by environment interactions generally do not exist. Water supply, as an important single determinant of the effect of the environment, was studied separately analysing data from selected locations. Under drought conditions, withholding irrigation reduced leaf and taproot growth and root-to-leaf ratio, decreased the percentage of sucrose in dry matter and resulted in an accumulation of α-amino N. Interactions between genotype and water supply did not occur for any of the parameters under study. A genotype-specific high α-amino N content, which might be of advantage for osmoregulation, did not improve the adaptation to drought. Differences in leaf maintenance or taproot-to-leaf ratio during drought also did not affect yield response. Due to the lack of interaction between genotype and harvest date as well as between genotype and irrigation it is concluded that harvest date or climatic factors of the growing region do not have to be taken into consideration when choosing a variety.     

Effects of water limitation on yield advantage and water use in wheat (Triticum aestivum L.)/maize (Zea mays L.) strip intercropping

Wheat (Triticum aestivum L.)/maize (Zea mays L.) strip intercropping is widely practiced in arid regions of northwestern China because of its high land use efficiency. However, its sustainability has been questioned because it consumes much more water than sole cropped wheat or maize. The present study was conducted to investigate the effects of water limitation on the yield advantage and water use of this system. Three field experiments were conducted in the Hetao Irrigation District in Inner Mongolia during the growing seasons of 2012–2014. Each experiment comprised two water applications, in which one was full irrigation and the other was a period of water limitation during the co-growth period of intercropping.The interspecific competition in wheat/maize intercropping was intensified by water stress. For water limitation applied during the wheat booting/maize V5 stage (Exp. I, second irrigation was not applied), the yield advantage of intercropped wheat (IW) over sole wheat was enhanced, whereas that of intercropped maize (IM) over sole maize was reduced compared with full irrigated treatments; for water limitation applied during the wheat jointing/maize V2 stage (Exp. II, first irrigation was not applied), the yield advantages of both IW and IM were greatly reduced; for water limitation applied during the wheat grain filling/maize V9 stage (Exp. III, third irrigation was not applied), the yield advantage of IW was slightly improved, whereas that of IM was reduced. The yield advantage of intercropping under limited irrigation was 25%, 3%, and 18% in Exps. I–III, respectively, whereas that under full irrigation ranged between 22 and 24%.Under well-watered conditions, wheat/maize intercropping used 24–29% more water than the weighted means of sole crops with the water use efficiency equivalent to sole crops. After the application of water limitation, 60 mm irrigation water was saved by intercropping every year, whereas the reduction of water use ranged from 25.1 to 70.8 mm; the changes in water use of intercropping relative to sole crops was reduced to 18–24%; the changes in water use efficiency stayed at nearly zero in Exps. I and III but decreased to a value of −13% in Exp. II. These results indicated that water limitation could be applied during wheat booting or filling stage in wheat/maize intercropping to save irrigation water in our study area.     

盐度对大麻哈鱼幼鱼肝脏组织学、非特异性免疫酶及消化酶活力的影响

为研究盐度对大麻哈鱼幼鱼非特异性免疫酶、消化酶活力及肝脏组织结构的影响,试验设置4个盐度组(0‰、8‰、16‰、24‰),周期42天,取肝脏和消化道分别测定非特异性免疫酶和消化酶活力,并观察肝脏组织结构变化。结果表明：大麻哈鱼幼鱼肝脏超氧化物歧化酶、谷胱甘肽过氧化物酶和过氧化氢酶活力变化趋势一致,随着盐度升高均呈现出先上升后下降的趋势,但其活力峰值不同;碱性磷酸酶活力随盐度升高呈现先升后降的趋势,而盐度对各组之间酸性磷酸酶活力无显著影响(P>0.05);盐度对消化道各种消化酶活力影响复杂且各种消化酶之间并未表现出整体效应;组织切片显示盐度0‰、8‰、16‰组肝脏结构正常,而盐度24‰组则呈现一定程度病变。推测体重1 g左右的大麻哈鱼降海洄游时比较适宜的盐度范围介于8‰~16‰之间。     

Suspended matter and bottom deposits in the maroni estuarine system (French Guiana)

The purpose of the research on the major rivers in French Guiana is identification and estimation of their contribution to estuarine and inshore continental shelf sedimentation. Results are reported of field studies on the Maroni river conducted during one rainy season and one dry season.The sands of the Maroni fluvio-estuarine system are subject to seasonal variations. During the dry season the sands were distributed in two groups on either side of the lle aux Pigeons, whereas during the rainy season, greater homogeneity was noted throughout the estuary. The sands gave evidence of a lengthy history including marine, continental and finally fluviatile stages. The play a part in sedimentation on the inner continental shelf.Fine sediments had uniform characteristics throughout the year. Mineralogic and elemental composition in the vicinity of Ile Portal indicated that they were different on either side of a limit separating the fluviatile and estuarine zones. Sediment groups were respectively autochtonal (upstream) and allochtonal (downstream), while the characteristics of the clay assemblage and elemental composition in the latter zone are evidence of an Amazon river origin. Their patterns showed evidence of a local stock that is quickly diluted by the mass of sediments derived from the Amazon river, the predominant source for the region.     

台风影响下海水养殖塘水环境响应特征分析

挑选2013—2017年对宁波影响较大的强降水型和非强降水型台风,基于台风影响期间宁波地区5个代表性海水养殖塘水环境因子观测资料（水温T、溶解氧DO、盐度S、酸碱度pH）,通过谐波分析和数理统计,以期探究台风期间海水养殖塘水环境因子的变化特征及关键影响因子。结果显示：（1）2阶谐波能反映养殖塘水体的T、pH和DO变化,3阶谐波能较好模拟S变化;（2）在台风影响关键期,水环境因子的谐波构成中短周期谐波的比重整体上升,强降水型台风短周期谐波的比重较非强降水台风高;（3）在相关性分析基础上,利用水环境和气象要素谐波构成及变化对比,可得T和DO变化主要受气温影响,强降水对S和pH影响显著。谐波方法能较好地模拟台风影响期间海水养殖塘水环境因子的变化特征,并为养殖塘水环境关键气象影响因子筛选提供新的思路。     

Temperature beat on a tidal flat: Potential cue for harpacticoid bloom

Temperature was recorded in the sediment on a tidal flat in the Fraser estuary (Canada) from February 15 to July 1985, and from February 19 to July 9 in 1986, with continuous recording thermographs. Within these periods, the abundance of an assemblage of harpacticoid copepods (Tisbe spp., Zaus aurelii, Harpacticus uniremis) was monitored bi-weekly by sampling the water column with a sled-sampler. Temperature time-series of both years showed the expected fortnightly beats in the daily temperature cycle. A reversal in the direction of the change of temperature in the sediment during exposure was observed on March 12 in 1985, and on March 1 in 1986. This reversal initiated the seasonal warming beat in the sediment when exposed at lower low waters, and is caused by the precessing of the timing of the lower low waters relative to the solar day. Blooming period of harpacticoids was centred on March 21 in 1985, and on March 12 in 1986. Closeness and apparent co-phasing of warming beat initiation and bloom onset suggest that the reversal in the direction of temperature change at lower low waters exposure could be a cue for harpacticoid blooming. The predictability of the timing of this clear signal in the thermal regime could provide the basis for an unequivocal definition of the link between harpacticoid abundance and temperature on tidal flats.