Bimodal Seasonal Cycle Research Articles

Seasonal Variation of Tropical Cyclone Genesis and the Related Large-Scale Environments: Comparison between the Bay of Bengal and Arabian Sea Sub-Basins

Using tropical cyclone data along with sea surface temperature data (SST) and atmospheric circulation reanalysis data during the period of 1980–2019, the seasonal variation of tropical cyclone genesis (TCG), and the related oceanic and atmospheric environments over the Arabian Sea (AS) and Bay of Bengal (BOB) are compared and analyzed in detail. The results show that TCG in both the BOB and AS present bimodal seasonal variations, with two peak periods in the pre-monsoon and post-monsoon season, respectively. The frequencies of TCG in the BOB and AS are comparatively similar in the pre-monsoon season but significantly different in the post-monsoon season. During the post-monsoon season of October–November, the TCG frequency in the BOB is approximately 2.3 times higher than that of the AS. The vertical wind shear and relative humidity in the low- and middle-level troposphere are the two major contributing factors for TCG, and the combination of these two factors determines the bimodal seasonal cycle of TCG in both the AS and BOB. In the pre-monsoon season, an increase in the positive contribution of vertical wind shear and a decrease in the negative contribution of relative humidity are collaboratively favorable for TCG in the AS and BOB. During the monsoon season, the relative humidity factor shows a significant and positive contribution to TCG, but its positive effect is offset by the strong negative effect of vertical wind shear and potential intensity, thus resulting in very low TCG in the AS and BOB. However, the specific relative contributions of each environmental factor to the TCG variations in the AS and BOB basins are quite different, especially in the post-monsoon season. In the post-monsoon season, the primary positive contributor to TCG in the AS basin is vertical wind shear, while the combined effect of vertical wind shear and relative humidity dominates in the BOB TCG. From the analysis of environmental factors, atmospheric circulations, and genesis potential index (GPI), the BOB is found to have more favorable TCG conditions than the AS, especially in the post-monsoon season.

Prolific Lightning and Thunderstorm Initiation over the Lake Victoria Basin in East Africa

AbstractThe Lake Victoria basin of East Africa is home to over 30 million people, over 200 000 of whom are employed in fishing or transportation on the lake. Approximately 3000–5000 individuals are killed by thunderstorms yearly, primarily by outflow winds and resulting large waves. Prolific lightning activity and thunderstorm initiation in the basin are examined using continuous total lightning observations from the Earth Networks Global Lightning Network (ENGLN) for September 2014–August 2018. Seasonal shifts in the intertropical convergence zone produce semiannual lightning maxima over the lake. Diurnally, solar heating and lake and valley breezes produce daytime lightning maxima north and east of the lake, while at night the peak lightning density propagates southwestward across the lake. Cluster analysis reveals terrain-related thunderstorm initiation hot spots northeast of the lake; clusters also initiate over the lake and northern lowlands. The most prolific clusters initiate between 1100 and 1400 LT, about 1–2 h earlier than the average cluster. Most daytime thunderstorms dissipate without reaching Lake Victoria, and annually 85% of clusters producing over 1000 flashes over Lake Victoria initiate in situ. Initiation times of prolific Lake Victoria clusters exhibit a bimodal seasonal cycle: equinox-season thunderstorms initiate most frequently between 2200 and 0400 LT, while solstice-season thunderstorms initiate most frequently from 0500 to 0800 LT, more than 12 h after the afternoon convective peak over land. More extreme clusters are more likely to have formed over land and propagated over the lake, including 36 of the 100 most extreme Lake Victoria thunderstorms. These mesoscale clusters are most common during February–April and October–November.

Variability and Geographical Origin of Five Years Airborne Fungal Spore Concentrations Measured at Saclay, France from 2014 to 2018

Airborne fungal spores (AFS) represent the major fraction of primary biological aerosol particles (PBAPs), and they are studied worldwide largely due to their important role within the Earth system. They have an impact on climate and human health, and they contribute to the propagation of diseases. As their presence in the air depends largely on studied ecosystems, a spore trap was used to monitor their atmospheric concentrations from 2014 to December 2018 in Saclay, a suburban area in the megacity of Paris. The main objective of this work was: (1) to understand the atmospheric variability of AFS in relation to different variables such as meteorological factors, agricultural practice, and (2) to identify their geographical origin by using a source receptor model. During our period of observation, 30 taxa have been identified under a light microscope. In order of importance, Ascospores, Cladosporium, Basidiospores, Tilletiopsis, Alternaria were found to be the most abundant types respectively (50.8%, 33.6%, 7.6%, 1.8%, and 1.3%) accounting for 95% of the atmospheric concentrations. We observed a general decrease associated with a strong interannual variability. A bimodal seasonal cycle was identified with a first maximum in July and a second in October. The main parameters driving the atmospheric concentration are temperature and precipitation. The daily variability is strongly activated by successive periods of hot weather and rainfall, multiplying the concentration by a factor of 1000 in less than 12 hours. Results from the source receptor model ZeFir point out unambiguous different origins of AFS due to specific sources impacting the observation site. Our study also indicated that a hydrological stress has a direct effect on the daily concentrations. This last point should be taken into account for every stressed ecosystem studied in a global warming context. This is particularly important for Mediterranean areas where water is a key control of the growth and dispersion of fungal spores.

Spatiotemporal variation of vertical particle fluxes and modelled chlorophyll a standing stocks in the Benguela Upwelling System

Abstract Marine particle fluxes from high productive coastal upwelling systems return upwelled CO2 and nutrients to the deep ocean and sediments and have a substantial impact on the global carbon cycle. This study examines relations between production regimes on the shelf and over the continental margin of the Benguela Upwelling System (BUS) in the SE Atlantic Ocean. Data of composition and timing of vertical particle flux come from sediment trap time series (deployed intermittently between 1988 and 2014) in the regions Walvis Ridge, Walvis Bay, Luederitz and Orange River. We compare their seasonal variability to modelled patterns of chlorophyll concentrations in a 3-D ecosystem model. Both modelled seasonal chlorophyll a standing stocks and sampled particle flux patterns are highly correspondent with a bimodal seasonal cycle offshore the BUS. The material in the particle flux in offshore traps is dominantly carbonate (40–70%), and flux peaks in offshore particle flux originate from two independent events: in austral autumn thermocline shoaling and vertical mixing are decoupled from coastal upwelling, while fluxes in spring coincide with the upwelling season, indicated by slightly elevated biogenic opal values at some locations. Coastal particle fluxes are characterized by a trimodal pattern and are dominated by biogenic opal (22–35%) and organic matter (30–60%). The distinct seasonality in observed fluxes on the shelf is caused by high variability in production, sinking behaviour, wind stress, and hydrodynamic processes. We speculate that global warming will increase ocean stratification and alter coastal upwelling, so that consequences for primary production and particle flux in the BUS are inevitable.

Comparison of simulated and reconstructed variations in East African hydroclimate over the last millennium

Abstract. The multi-decadal to centennial hydroclimate changes in East Africa over the last millennium are studied by comparing the results of forced transient simulations by six general circulation models (GCMs) with published hydroclimate reconstructions from four lakes: Challa and Naivasha in equatorial East Africa, and Masoko and Malawi in southeastern inter-tropical Africa. All GCMs simulate fairly well the unimodal seasonal cycle of precipitation in the Masoko–Malawi region, while the bimodal seasonal cycle characterizing the Challa–Naivasha region is generally less well captured by most models. Model results and lake-based hydroclimate reconstructions display very different temporal patterns over the last millennium. Additionally, there is no common signal among the model time series, at least until 1850. This suggests that simulated hydroclimate fluctuations are mostly driven by internal variability rather than by common external forcing. After 1850, half of the models simulate a relatively clear response to forcing, but this response is different between the models. Overall, the link between precipitation and tropical sea surface temperatures (SSTs) over the pre-industrial portion of the last millennium is stronger and more robust for the Challa–Naivasha region than for the Masoko–Malawi region. At the inter-annual timescale, last-millennium Challa–Naivasha precipitation is positively (negatively) correlated with western (eastern) Indian Ocean SST, while the influence of the Pacific Ocean appears weak and unclear. Although most often not significant, the same pattern of correlations between East African rainfall and the Indian Ocean SST is still visible when using the last-millennium time series smoothed to highlight centennial variability, but only in fixed-forcing simulations. This means that, at the centennial timescale, the effect of (natural) climate forcing can mask the imprint of internal climate variability in large-scale teleconnections.

Seasonality of North Atlantic phytoplankton from space: impact of environmental forcing on a changing phenology (1998–2012)

Seasonal pulses of phytoplankton drive seasonal cycles of carbon fixation and particle sedimentation, and might condition recruitment success in many exploited species. Taking advantage of long-term series of remotely sensed chlorophyll a (1998-2012), we analyzed changes in phytoplankton seasonality in the North Atlantic Ocean. Phytoplankton phenology was analyzed based on a probabilistic characterization of bloom incidence. This approach allowed us to detect changes in the prevalence of different seasonal cycles and, at the same time, to estimate bloom timing and magnitude taking into account uncertainty in bloom detection. Deviations between different sensors stressed the importance of a prolonged overlap between successive missions to ensure a correct assessment of phenological changes, as well as the advantage of semi-analytical chlorophyll algorithms over empirical ones to reduce biases. Earlier and more intense blooms were detected in the subpolar Atlantic, while advanced blooms of less magnitude were common in the Subtropical gyre. In the temperate North Atlantic, spring blooms advanced their timing and decreased in magnitude, whereas fall blooms delayed and increased their intensity. At the same time, the prevalence of locations with a single autumn/winter bloom or with a bimodal seasonal cycle increased, in consonance with a poleward expansion of subtropical conditions. Changes in bloom timing and magnitude presented a clear signature of environmental factors, especially wind forcing, although changes on incident photosynthetically active radiation and sea surface temperature were also important depending on latitude. Trends in bloom magnitude matched changes in mean chlorophyll a during the study period, suggesting that seasonal peaks drive long-term trends in chlorophyll a concentration. Our results link changes in North Atlantic climate with recent trends in the phenology of phytoplankton, suggesting an intensification of these impacts in the near future.

Photoacclimation of picophytoplankton in the central Cantabrian Sea

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 493:43-56 (2013) - DOI: https://doi.org/10.3354/meps10549 Photoacclimation of picophytoplankton in the central Cantabrian Sea Evaristo Vázquez-Domínguez*, Xosé Anxelu G. Morán, Angel López-Urrutia Spanish Institute of Oceanography (IEO), Oceanographic Center of Xixón, Camín de L’Arbeyal, s/n, 33212 Xixón, Asturies, Spain *Email: ristovazquez@gmail.com ABSTRACT: Photoacclimation of picophytoplankton was studied in the mixed layer of 3 stations in the central Cantabrian Sea (southern Bay of Biscay). Picophytoplankton chl a:carbon ratios (θ) presented minimum values during summer, when irradiance, temperature, and biomass of prokaryotes reached maximum values and inorganic nutrient concentrations were low. Conversely, the maximum θ were reached during winter, coincident with lowest annual irradiance but maximum concentration of inorganic nutrients and higher relative biomass of eukaryotes. Changes in θ were modeled using irradiance as an independent variable. Exponentially decreasing functions of θ with irradiance were significant only when the mean temperatures in the mixed layer were above 14°C. These functions presented light-saturated minimum ratios (θmin) that decreased linearly with temperature and low-light maximum ratios (θmax) that increased exponentially with temperature. Such relationships were used to establish an empirical model that reproduced the seasonality of picophytoplankton θ in the mixed layer, with minima in summer and maxima in winter. A maximum potential θ, θN,T-max, was determined to estimate picophytoplankton growth rates in the central Cantabrian Sea. Combinations of picophytoplankton growth rates and biomass in the mixed layer were used to estimate areal picophytoplankton primary production rates in the euphotic zone that presented a bimodal seasonal cycle, with maxima in late winter (ca. 100 mg C m-2 d-1) and in late autumn (>200 mg C m-2 d-1) and mean annual values around 120 mg C m-2 d-1. KEY WORDS: Light · Temperature · Nutrients · Picophytoplankton · Chl a:carbon ratio · Modeling Full text in pdf format PreviousNextCite this article as: Vázquez-Domínguez E, Morán XAG, López-Urrutia A (2013) Photoacclimation of picophytoplankton in the central Cantabrian Sea. Mar Ecol Prog Ser 493:43-56. https://doi.org/10.3354/meps10549 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 493. Online publication date: November 20, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

A review of observed and projected changes in climate for the islands in the Caribbean

Observed and projected changes in climate have serious socio-economic implications for the Caribbean islands. This article attempts to present basic climate change information—based on previous studies, available observations and climate model simulations—at spatial scales relevant for islands in the Caribbean. We use the General Circulation Model (GCM) data included in the Coupled Model Intercomparison Project phase 3 (CMIP3) and the UK Hadley Centre regional climate model (RCM) data to provide both present-day and scenario-based future information on precipitation and temperature for individual island states. Gridded station observations and satellite data are used to study 20th century climate and to assess the performance of climate models. With main focus on precipitation, we also discuss factors such as sea surface temperature, sea level pressure and winds that affect seasonal variations in precipitation. The CMIP3 ensemble mean and the RCM successfully capture the large-scale atmospheric circulation features in the region, but show difficulty in capturing the characteristic bimodal seasonal cycle of precipitation. Future drying during the wet season in this region under climate change scenarios has been noted in previous studies, but the magnitude of change is highly uncertain in both GCM and RCM simulations. The projected decrease is more prominent in the early wet season erasing the mid-summer drought feature in the western Caribbean. The RCM simulations show improvements over the GCM mainly due to better representation of landmass, but its performance is critically dependent on the driving GCM. This study highlights the need for high-resolution observations and ensemble of climate model simulations to fully understand climate change and its impacts on small islands in the Caribbean.

Seasonal dynamics of rotifer in a seasonal fishing moratorium lake - Lake Erhai, Yunnan Province, China

于2009年2-11月对洱海轮虫进行月际采样,分析洱海轮虫的多样性及其群落结构季节动态特征.洱海作为一个高原湖泊,其轮虫种类组成仍然呈现出热带-亚热带的主要特征.本研究共鉴定轮虫68种,多数种类为广布性或暖水性种类,隶属17科25属,异尾轮属、腔轮属和臂尾轮属是种类最多的三个属,占鉴定轮虫种类的37%.Lecane arcuata和Trichocera inermis为我国新纪录种.轮虫生物量的季节分布呈双峰型,并分别出现在休渔期的中期和捕鱼期前期.在休渔期中期,轮虫主要以前节晶囊轮虫为优势种;在捕鱼期前期,轮虫先以螺形龟甲轮虫和广生多肢轮虫为优势,后以前节晶囊轮虫为优势.季节性休渔不仅使鱼类对轮虫的捕食压力出现季节性变化,而且还通过影响枝角类的群落结构改变枝角类对轮虫的竞争压力.在捕食和竞争的双重作用下,轮虫主要以大型杂食性种类——前节晶囊轮虫为优势种类,并呈现双峰型的季节分布模式.;Rotifers were sampled monthly from February to November in 2009 in Lake Erhai, Yunnan Province, China, in order to study their diversity and seasonal dynamics. Lake Erhai has a rotifer composition with tropical-subtropical characteristics:68 species belonging to 25 genera of 17 families were identified, the majority of which were eurythermal or mesophilic. The genera of Trichocerca, Lecane and Brachionus were more abundant than others, accounting for 37% of the total community. Lecane arcuata and Trichocera inermis are new records in China. Biomass of the rotifer communities in Lake Erhai exhibited a bimodal seasonal cycle. An increase occurred during spring from low winter levels to an annual maximum in the mid fishing moratorium and a second increase in the early fishing season. In the mid fishing moratorium, the rotifer biomass was dominated by Asplanchna priodonta; while in the early fishing season, it was dominated by the small-sized Keratella cochlearis and Polyarthra vulgaris, then by A. priodonta again. The seasonal fishing moratorium affected not only the predation pressure on rotifers, but also competitive pressure on rotifer through influencing the community structure of Cladocera. Through the influence of predation and competition, rotifers were dominated by large omnivorous A. priodonta, which showed a bimodal seasonal distribution pattern.

Complex seasonal cycle of ecohydrology in the Southwest United States

This study investigates the causes for, and distribution of, unimodal versus bimodal seasonal cycle of vegetation greenness in the Southwest United States using extensive site observations, climate data, satellite data, and the Lund‐Potsdam‐Jena (LPJ) vegetation model. Peak vegetation greenness is achieved in a clockwise manner across the Southwest, beginning in spring in the Sonoran Desert following winter rains, then in Utah‐Colorado with snowmelt/summer rains, and finally in New Mexico–eastern Arizona with late summer monsoon rains. At high elevations, spring‐summer snowmelt is critical for supplying the necessary soil moisture to trigger vegetation growth. A bimodal seasonal cycle of vegetation greenness is evident in satellite data and LPJ simulations across eastern Arizona and western New Mexico, characterized by peaks during late spring–early summer and late summer–early autumn. This bimodal green‐up remains a pressing paradox for which many competing hypotheses exist. The mechanism for this seasonal pattern is demonstrated using LPJ and observational data and is found to deviate from the traditional pulse‐reserve paradigm. This paradigm states that rainfall events in arid lands produce nearly immediate pulses of vegetation growth and accumulation of reserves but does not consider cold dormancy, time‐lagged vegetation responses, or rainfall seasonality. The following soil moisture based mechanism for bimodal greening is proposed. The initial peak in vegetation greenness during late spring–early summer results from a break in cold dormancy and benefits from the gradual winter‐long accumulation of deep soil moisture from weak synoptic rain events and snowmelt in colder regions. Limited precipitation and ongoing transpiration, from the initial vegetation greening, trigger a midsummer drying of the soil and a consequential minimum in vegetation activity. Later, pulses of monsoon rainfall in late summer–early autumn support the secondary greening, although significant runoff of brief, intense rainstorms and substantial soil evaporation limit moisture to the upper soil layers.

Seasonal variation in circulation and water mass distribution on the Ross Sea continental shelf

Changes in water mass distribution and horizontal circulation due to seasonal influences on the Ross Sea continental shelf are investigated using a circumpolar numerical model. An anticyclonic circulation cell that extends across the open shelf and into the ice shelf cavity is formed in the model. The increased east–west density gradient caused by the strong brine release in the Ross Sea polynya in winter results in an intensification of this anticyclonic cell from 1.5 Sv to 2.5 Sv. This supports the concept of a thermohaline-driven horizontal circulation on the Ross Sea continental shelf. In addition to a temporal change in the circulation strength, the changes in the density structure lead to complex temporal and spatial variability in the circulation around Ross Island. Due to seasonal variation in circulation strength and water temperatures, the area averaged basal melt rate of 25 cm a−1 shows a bimodal seasonal cycle ranging from 20–28 cm a−1, with maxima in March and August.

Asynchronous Male and Female Gonadal Cycles and Plasma Steroid Concentrations in a Viviparous Lizard,Niveoscincus ocellatus(Scincidae), from Tasmania

The reproductive cycle in males of the skink,Niveoscincus ocellatus,is characterised by testicular development during summer, followed by mating in autumn. Plasma testosterone concentrations show a bimodal seasonal cycle, with the major peak (18.6±1.2 ng/ml) in late summer/autumn and a minor peak (7.4±1.0 ng/ml) at spring emergence. In contrast to the males, the females have a gonadal cycle in which mating is temporally dissociated from peak development of the gonads: ovulation occurs in spring and the young are born in summer. Fresh mating marks on females in spring indicate that at least part of the population mates for a second time after spring emergence. In females, plasma estradiol concentrations are significantly elevated (956±214 pg/ml) through vitellogenesis and are highest (1241±175 pg/ml) during the preovulatory phase. Plasma progesterone concentrations rise during gestation to 6.5 ± 1.5 ng/ml, but fall in the final stage of gestation to 1.6 ± 0.2 ng/ml. There is minimal atresia of vitellogenic follicles, suggesting that clutch size is determined when the follicles are recruited for vitellogenesis.

Ecology ofVibrio cholerae in the freshwater environs of Calcutta, India

Seasonal incidence ofVibrio cholerae was monitored for a year in a man-made freshwater lake, an open sewage canal, and a pond composed of rainwater accumulations, located in Calcutta.V. cholerae was found in all sites. It exhibited a distinct bimodal seasonal cycle in the lake with a primary peak in August-September and a secondary peak in May-June. Correlation with environmental parameters revealed that temperature and, to a certain extent, pH were the important factors governing the densities ofV. cholerae. In the lake, sediment samples harbored high densities ofV. cholerae immediately after months when peak counts were observed in plankton, suggesting a cycle of cells between sediment and water. At the other sampling areas, no defined seasonality was observed. Instead, high counts ofV. cholerae were observed at these severely polluted sites throughout the study period, including the winter months. All the 15 water samples passed via the ligated loop of rabbits yielded pure cultures ofV. cholerae, indicating that the rabbit intestine selects outV. cholerae from a mixed flora. Uniformly high isolation rates ofV. cholerae were observed from brackish water and freshwater species of export quality prawns.V. cholerae was found to be abundant and was represented by 32 individual Louisiana State University (LSU) serovars, including two new serovars. The 01 serovar could not be isolated from any of the samples examined in this study. It was concluded thatV. cholerae non-01 is common in the freshwater environs of Calcutta.

Interannual Variation in Sea Level near Truk Island—A Bimodal Seasonal Cycle

Abstract The relationship between typical seasonal and interannual variations in Truk sea level is discussed. Periods of extreme low sea level occur episodically, at the same time that El Nino occurs in the eastern tropical Pacific. The episodes have a well-defined phase relative to the seasons and a persistence of one year. They mimic an annual cycle, but they do not repeat every year. Nevertheless, they distort the long-term mean seasonal cycle because they are very energetic. Complex demodulation shows that the amplitude of the annual oscillation is bimodal, the larger amplitude occurring during the episodes of low sea level. The phase is stable only when the amplitude is large. The amplitude and phase of the semiannual oscillation are stable; the range is approximately one-third as large as that of the interannual episodes. Thus, the seasonal cycle is bimodal in the sense that it is dominated by either the annual episode or the stable semiannual oscillation. The climate-related sea-level variation at ...

Continuous plankton records: seasonal variations in the distribution and abundance of plankton in the North Atlantic Ocean and the North Sea

Charts are presented of the seasonal variations in the distribution of four phytoplankton and five zooplankton taxa in the North Atlantic and the North Sea. The main factors determining the seasonal variations appear to be the distribution of the main overwintering stocks, the current system and, in some instances, temperature control of the rate of population increase. Information is presented about the variation with latitude (over the range from 34° N to 65 ° N) of the seasonal regime of the plankton. On the assumption that there is a relationship between nutrient supply and vertical temperature stratification the main features of this variability can be interpreted. In the south (to about 43° N) nutrient limitation plus grazing appear to be dominant, resulting in a bimodal seasonal cycle of phytoplankton. North of about 60° N the system appears to be limited by the size of the phytoplankton stocks being grazed primarily by Calanus Finmarchicus and Euphausiacea. In an extensive zone, from about 44° N to 60° N, it would appear that the spring bloom of phytoplankton is under-exploited by grazing while in summer the zooplankton graze the daily production of the phytoplankton, the stocks of which are probably maintained by in situ nutrient regeneration. The implications, for at least this mid-latitude zone, that rates and fluxes of processes, as opposed to density dependent interactions between stocks, play a major role in the dynamics of the seasonal cycle is consistent with previously reported observations suggesting that physical environmental factors play a major role in determining year-to-year fluctuations in the abundance of the plankton.

ORGANIC AGGREGATES IN SEAWATER AND THE DYNAMICS OF THEIR FORMATION AND UTILIZATION

Much of the nonliving particulate organic matter in seawater consists of delicate, plate‐like aggregates ranging in size from about 5 µ to several mm in diameter. The aggregates are amorphous matrices containing both organic and inorganic materials, with inclusions of bacteria and phytoplankton. Descriptive information herein deals primarily with a two‐year series of observations in Long Island Sound. A consistent bimodal seasonal cycle has been found, with peaks in winter and early summer. These aggregates appear to be formed mainly by adsorption of dissolved organic matter on bubbles and other naturally occurring surfaces in the sea, a process readily duplicated under experimental conditions. Naturally occurring aggregates provide a substrate for bacterial growth and probably food for animals. They are present during certain seasons when phytoplankton is scarce and probably serve an important function as supplementary food for zooplankton under such circumstances. The presence of aggregates is an oceanic as well as a coastal phenomenon and is believed to have general ecological significance. A concept is developed that the reversible reaction between dissolved and particulate matter tends to stabilize the marine association, and there are suggestions of community adaptation in the development of this system.