Showing papers on "Productivity (ecology) published in 1981"

Productivity of Desert Ecosystems

Abstract: Primary production in desert ecosystems is limited by precipitation, nutrient availability (especially nitrogen), and the species' production potential. Plant biomass provides food for consumers that occupy several trophic levels. The resultant transfer of energy and nutrients is also water-limited as are rates of decomposition and activities of decomposer organisms. (Accepted 20 February 1981)

Structure and Function of Two Antarctic Terrestrial Moss Communities

Abstract: Two bryophyte-dominated communities in the maritime Antarctic are analyzed in terms of the transfer and standing crops of organic matter within them A moss turf dominated by Polytrichum alpestre and Chorisodontium aciphyllum and a moss carpet composed of Calliergon sarmentosum, Calliergidium austro-stramineum, and Drepanocladus uncinatus with the liverwort Cephaloziella varians were investigated at Signy Island, South Orkney Islands Biomass, respiration, and production data for the primary producers (mosses, lichens, liverworts, and algae), for the fauna (Protozoa, Rotifera, Tardigrada, Nematoda, Acari, and Collembola), and for the microflora were synthesized, and annual rates of consumption, egestion, assimilation, and production were derived The two communities showed similar levels of productivity, trophic structure, and efficiencies of organic matter transfer, but different Collembola and Acari standing crops, turnover of mosses, and accumulation of dead organic matter These features are discussed in relation to the role of biotic and abiotic variables in determining community structure and function

Productivity Dynamics of a Native Temperate Grassland in Argentina

Abstract: Studies of aerial net primary productivity (ANPP) were made on a grassland that had been excluded from livestock grazing for four years. ANPP was calculated by summation of individual species and corrections based on fluctuations of standing dead litter. The grassland produced a minimum of 4 kg of dry material ha-' d1' in the fall and a maximum of 30 kg of dry material -ha 1d - during the spring. Salado River Basin occupies an area of 5,800,000 ha in Buenos Aires Province, Argentina, 80% of which is covered by native grassland utilized for cattle production. The proximity of the area to the city of Buenos Aires makes it important as a source of beef to this large area of population. The general aspect of the basin is that of an extensive plain with little or no slope. This results in a great number of permanent ponds and areas subjected to frequent flooding. However, vegetation of the area also suffers from severe summer droughts because of shallow soils. Climate is temperate and humid. Annual precipitation is 900 mm of rainfall that is evenly distributed throughout the year. No snow deposition occurs. This mild weather permits the grasses to maintain productivity during the entire year. The objectives of this study were to describe the (1) dynamics of the aerial biomass and (2) the dynamics of the aboveground net primary productivity (ANPP) of a native grassland of the Salado River Basin and of its major species throughout an entire year. The study was conducted in one of the most conspicuous communities of the basin. This community was described by Leon (1975) using Braun-Blanquet (1950) techniques and named Piptochaetium montevidense, Ambrosia tenuifolia, Eclipta bellidioides, and Metha pulegium.

Changes in the biomass and productivity of woodlands in the Sengwa Wildlife Research area, Zimbabwe.

Abstract: (1) Changes in biomass and annual production measured over the period 1972 to 1976 in four woodlands, the miombo, the Sengwa/Lutope riverine, the Manyoni riverine and the mopane woodland, are described. (2) The greatest changes in biomass were recorded in the miombo woodland where it is estimated that the biomass decreased by 45%. The biomass of the Sengwa/Lutope riverine, a woodland with three strata, increased by 14%, whilst that of the Manyoni riverine changed little. The biomass of the mopane woodland decreased by over 6%. (3) The annual production of the miombo, the Manyoni riverine and the mopane woodlands decreased between 1972 and 1976, whereas that of the Sengwa/Lutope riverine woodland increased. (4) The change in the biomass of the miombo woodland was primarily a result of the removal by elephant of large trees which were not replaced due to the effects of elephant and fire. (5) The increase in biomass of the Sengwa/Lutope riverine woodland was a result of recruitment to both the tree and shrub layers. The tree biomass increased by 394%, and the shrub biomass by 207% but the biomass of the upper canopy trees decreased by 10%. (6) The decrease in biomass of the mopane woodland which is seldom affected by fierce fires, was almost certainly due to the effects of elephant. (7) Due to the opening up of the canopy and the coppicing of damaged trees, more browse is now in reach of the smaller browsing animals in all woodlands except the Manyoni riverine. (8) Elephant appear to have been responsible for the decreases in biomass but fire has also contributed.

Phenotypic and genotypic components of growth and reproduction in typha latifolia: experimental studies in marshes of differing successional maturity'

Abstract: The objective of this study was to separate the genotypic and phenotypic variation in biomass allocation for populations of Typha latifolia from habitats of differing successional maturity. Field studies revealed that the OPEN marsh population of T. latifolia suffered high levels of ramet mortality over winter and had rapid growth in ramet numbers during the growing season. In contrast, the WOODS marsh population suffered predominantly from growing-season mortality with little ramet death over winter. The CATTAIL marsh population was intermediate in mortality patterns to the other two populations. Tissue nutrient analyses and fertilization experiments revealed that T. latifolia in the OPEN marsh was principally nutrient limited while T. latifolia in the WOODS marsh was light limited. The CATTAIL marsh population was exposed to conditions of nutrients and light intermediate to the other populations. Field studies of 14C fixation and allocation showed that both sexual and vegetative reproduction consisted of greater percentages of biomass production in the OPEN marsh population than in the CATTAIL or WOODS marsh populations. Ramets in the CATTAIL and WOODS marsh populations allocated a greater percentage of their fixed carbon to growth of the parent ramet. Allocation to roots was greatest in the OPEN marsh population and experiments showed this response to result from low nutrient availability. Leaf biomass was a fixed percentage of the total biomass under all conditions but the leaf volume:leaf mass ratio was greatest in the WOODS marsh population. Experiments revealed that the differences in leaf volume:mass were principally the result of light availability, but that decreased wind exposure also contributed to the high leaf volume:mass ratio. Differences in biomass allocation under uniform garden conditions indicated biotypic differences among populations such that habitats exposed to high levels of disturbance contained biotypes with high allocation to sexual reproduction. In contrast, the biotype from the habitat with the most intense level of density stress (WOODS-CATTAIL marsh biotype) allocated more biomass to root production, a trait potentially important for competition. Transplantation of biotypes into natural habitats showed that under nutrient-limiting conditions the WOODS-CATTAIL marsh biotype was more productive than the OPEN marsh biotype. This difference resulted from differences in allocation patterns whereby the OPEN biotype allocated a greater percentage of biomass to rhizome storage for sexual reproduction and the WOODS-CATTAIL biotype allocated more to root growth. Under light-limiting conditions no differences in productivity between biotypes occurred. It is concluded that both genotypic and phenotypic variation in biomass allocation contribute to the growth and reproduction of T. latifolia over a broad range of habitats differing in successional maturity.

Biomass and production of an aspen-mixed hardwood-spodosol ecosystem in northern Wisconsin.

Abstract: Total biomass of an aspen – mixed hardwood – spodosol ecosystem in northern Wisconsin, U.S.A., was 197 t/ha and net primary production was 11.5 t/ha per year. Populustremuloides Michx. accounted fo...

The epilithic periphyton community: a five-lake comparative study of community productivity, nitrogen metabolism and depth-distribution of standing crop: With 2 figures and 3 tables in the text

Abstract: (1981). The epilithic periphyton community: a five-lake comparative study of community productivity, nitrogen metabolism and depth-distribution of standing crop. SIL Proceedings, 1922-2010: Vol. 21, No. 1, pp. 346-352.

Biomass method for measuring productivity of Echlonia radiata, with the potential for adaptation to other large brown algae

Abstract: A solution is proposed to the problem of converting measurements of growth in length of E. radiata to estimates of biomass production. It is shown that production can be calculated by multiplying biomass per unit length (in the zone of maximum biomass) by the increase in length of the primary blade. E. radiata has three stages of growth: (i) a simple strap-shaped primary blade; (ii) secondary blades growing from the primary; (iii) tertiaries arising from the secondaries in the mature plant. Distribution of biomass was determined by making transverse cuts across the primary blade and weighing the segments together with all attached secondary and tertiary blades. Plants were divisible into a zone where secondaries and tertiaries were increasing in size, a zone where they were at maximum size, and a zone where they were eroding. Biomass per unit length was calculated for the zone of maximum biomass, and when multiplied by the growth in length gave a good estimate of biomass production. Adaptation of this method to other large brown algae of the Laminariales is proposed.

The effects of climatic pattern on lichen productivity: Cetraria cucullata (Bell.) Ach. in the arctic tundra of northern Alaska.

Abstract: The climatic control of productivity for two populations of the lichen Cetraria cucullata (Bell.) Ach. growing in the arctic tundra of northern Alaska (70°28′N, 157°23′W) was examined. Respiratory losses of carbon vary with tissue temperature, tissue water content, and time since wetting. Potential net photosynthetic gains of carbon are affected by photon flux density, tissue temperature, and water content. The net CO2 exchange responses of populations growing on ridge tundra and on upland tundra differ and these differences reflect possible adaptation to the normal environmental regimes in the two habitats. Simulation of the lichen's net carbon balance using continuous hourly records of photon flux density, temperature, and water content for the unusually dry period June 28 through July 17, 1977 show that lichen biomass is actually lost during climatic regimes leading to frequent but short periods of lichen metabolic activity. This result is confirmed by the negative relative growth rates measured for C. cucullata over the same monitoring period. This observed loss of biomass may be attributable to depletion of carbon reserves to reactivate dormant metabolism without sufficiently long periods favorable for net photosynthetic activity to replenish the lost reserves. These results illustrate that environmental limits exist on the success of the dormancy strategy characteristic of lichen and moss carbon metabolism.

Biological and physical aspects of a coastal upwelling event observed during March-April 1974 off northwest Africa☆

Abstract: A description of the time scales of the physical and biological fields of a coastal upwelling event observed during March and April 1974 near 21°40′N off the coast of Mauritania is given from concurrent measurements of wind, current, temperature, salinity,chlorophyll- a , primary productivity, and nutrients. At a mid-shelf site the time lag between the onset of strong, equatorward winds and a significant increase in the offshore component of the near-surface currents was about 1 day. Nutrient-rich surface water was observed near the coast about 4 days after the initiation of the wind event, but because of the rates associated with the biological measurements, the time scale for the occurrence of large quantities of nutrient in the surface layer might have been less than 4 days. Despite the high nutrient concentrations in the nearshore region, the primary productivity remained low until the strength of the winds decreased about 10 days after the event began. The strong winds and offshore currents combined to produce a mixed layer considerably deeper than the euphotic zone. When the intensity of the equatoward winds and the offshore component of the near-surface current decreased, the upper ocean became stratified, the nutrients diminished, and the primary productivity increased. The productivity remained high for 2 to 3 days.

Primary productivity and the flux of dissolved organic matter in several marine environments

Abstract: Primary productivity and the flux of DO14C, dissolved saccharides (DSAC) and dissolved free primary amines (DFPA) were followed in the Sargasso Sea, Caribbean and upwelling waters of Peru. Average carbon fixation rates were 42.8, 292.8 and 4791.6 mg C m-2 d-1, respectively, with nocturnal respiration rates ranging from 9.8–16.3% of gross photosynthesis for the 3 areas. The release of DO14C, as a percentage of the total carbon fixed in photosynthesis, was non-detectable in the Sargasso Sea, and 3.2 and 4.4% for the Caribbean and Peruvian phytoplankton communities. Few significant changes in DSAC concentrations were recorded over a 36-h incubation period in the Sargasso Sea and Caribbean stations, whereas light-dependent accumulations of DSAC and DFPA were noted in Peruvian stations which were strongly correlated with total phytoplankton productivity. In the Peruvian stations, the average accumulation rate was 234 mg DSAC-C m-2h-1 while the average rate of nocturnal decomposition was 141 mg DSAC-C m-2h-1; diurnal and nocturnal rates of DFPA accumulation and decomposition were similar (2 mg DFPA-C m-2h-1). These data were used to calculate bacterial production in the upwelling waters of Peru. A general discussion of 14C-technique and routine analytical techniques for DSAC analysis is presented, as DSAC flux exceeded DO14C flux by 17-fold in coastal Peruvian stations.

Bivalve production and food chain efficiency in an experimental nursery system

Abstract: An experiment was performed to assess the productivity, food chain efficiency and nitrogen conversion efficiency of a semi-closed nursery system for bivalve spat held in upwelling columns. Algal blooms were encouraged by nutrient enrichment of onshore tanks and maintained for short periods under grazing pressure from bivalves.

Allochthonous plant litter as a source of organic material in an oligotrophic lake (Llyn Frongoch)

Abstract: The importance of airborne plant litterfall as a source of organic material was evaluated for a small oligotrophic lake. The airborne plant litter input was estimated to be 100 kg yr−1 (45 kg C. yr−1), which represents approximately 5% of the phytoplankton productivity. The quantity of plant litter entering the lake followed an exponential decline with distance from the shore.

Biomass, Productivity and Succession in the Scrub of the Doñana Biological Reserve in Southwest Spain

Abstract: The Donana Biological Reserve is located between 36°55′ and 37°3′ N latitude and 6°16′ and 6°34′ W longitude on the western side of the Guadalqivir River in southwestern Spain.

The streamside effect in a Carex lyngbyeiestuarine marsh: The possible role of recoverable underground reserves

Abstract: In a comparison of streamside and back marsh stands of Carex lyngbyei in an Oregon estuarine marsh, the maximum biomass and net annual aerial primary productivity of the streamside stands were 50% higher. Aerial productivity rates on a unit of biomass basis were similar except during the late winter-early spring period and in the fall. Studies of recoverable underground photosynthate reserves coupled with the net aerial primary productivity measurements indicate the timing of growth and the mobilization of reserves were important factors in the streamside effect (greater biomass and net annual aerial primary productivity).

Mass Bloom of the Alga Cladophora prolifera in Bermuda: Productivity and Phosphorus Accumulation

Abstract: The mass development of Cladophora in Bermuda inshore waters has been linked with eutrophication, but comparative nutrient determinations do not substantiate this. Indeed phosphate concentrations are even lower than in offshore waters. This may be due to geochemical processes or to removal of phosphate by the Cladophora mats. Field and laboratory experiments investigating the influence of phosphorus levels on productivity and phosphorus uptake in Cladophora show that: (1) Cladophora is able to lower very high phosphate concentration to the levels observed in Bermuda inshore waters, (2) Phosphate concentrations far in excess of those in oligotrophic Bermuda waters do not increase the productivity of Cladophora, (3) Cladophora previously grown under oligotrophic conditions accumulated surplus phosphorus even at extremely high phosphate concentrations. The spread of Cladophora can be explained by its competitive advantage (e.g. tolerance to H2S and anaerobic conditions) rather than by enhanced production due to increased phosphate concentrations. The morphological and physiological properties of Cladophora make it potentially useful for waste treatment. The low biomass production would limit effectiveness. Introduction or by the bioaccumulation of phosphorus by the exten, ,. f . ,~ , sive Cladophora mats in Harrington Sound. Since 1966, Cladophora prolifera (Roth) Kützing (Clado* * phorales), apparently new to the area, has spread rapidly We have investigated the effect of increasing phosphate in Bermuda inshore waters. Bach and Josselyri (1978,1979) levels on the productivity and the P-binding capacity of suggested that the mass development of unattached alga Cladophora. Since such processes might favour the self is due to eutrophication from sewage and agricultural purification of polluted waters and could even be useful land riuirpff but nutrient ^terminations dp not show enfor sewage treatment in coastal areas, we have used higher hanced nutrient levels in inshore waters (Morris et al phosphate concentrations than could ever be expected 1977, Barnes and v. Bedungen 1978). Even in the enin coastal waters, closed Harrington Sound, adjacent to densely populated areas and with extensive Cladophora mats, nutrient concentrations are only Slightly higher than in unpolluted Material and Methods exposed 'control' areas (Whalebone Bay). Phosphate con^ ̂ measurements on phosphate and oxygen exchange centrations are, i* fact, even lower in Harrington Sound ^ Cladohomm^ md of isolated plants, were than to the control area, or in the open sea off Bermuda. —̂ ß ^ ̂ a ̂ ^ ^ § Phosphate concentrations are so low that they may limit productivity (Morris et al 1977). One explanation for these -^ — observations could be the removal of phosphorus from * Carried out as part of the research program SFB 95, Univerthe water either by geochemical processes (Berner 1974) sity of Kiel 0006-8055/81/0024-0419302.00' » © by Walter de Gruyter & Co. · Berlin ' New York 420 Schramm and Booth: Cladophora in Bermuda: Productivity and phosphorus accumulation depth of 2 m using plastic enclosures as described by Schramm and Martens (1976). 02 exchange, irradiation and temperature were recorded continuously. Phosphate concentrations in the seawater were determined at approximately four hours intervals. Additional phosphorus was supplied in the form of K2HP04. All plant material used in laboratory experiments was collected from this location. For the laboratory experiments carried out in Kiel, the plants were airfreighted and arrived in Kiel within 24 hrs of collection. They were maintained in a 7001 aerated seawater aquarium at 22 °C, light 28 W/m (Hg lamp Type OSRAM HQI-IS) with a diurnal rythm of 14 hrs light and 10 hrs dark. The seawater medium of 36%0 salinity was achieved by the addition of sea salt to 18%0 Baltic seawater. Sets of subsamples of relatively homogeneous algal material were used for each of the laboratory experiments. Similar sized (~ 300 mg wet weight) portions subdivided from each of 10—20 clumps of healthy looking Clado· phora were placed into aerated seawater and maintained for 2 days, then checked for oxygen production to give the initial or 'normal' value for that particular set of subsamples. Any set deviating by more than 10% from the mean for the series was discarded. The use of wide based glass vessels, together with the subdivision of clumps detailed above, reduced the effects of shading. In the laboratory productivity was determined by measuring the 02 output (Winkler-method), C uptake or growth rates (increase in wet weight). For the measurements of 02 production, homogeneous plant material was incubated for 30 min in rotating glass bottles, in a water bath illuminated at 85 W/m. This irradiance is above light saturation for Cladophora which in the laboratory occurred at 30 W/m. For the laboratory investigations involving a series of phosphate concentrations, low phosphate, filtered (0.2ìéç), open Baltic seawater, brought to 36 %0 S by the addition of sea salt, was adjusted to the selected phosphate concentration by the addition of K2HP04. The phosphorus content of the culture medium plant material was measured either by chemical analysis (Koroleff 1976), or using radioactive phosphorus. For direct determination of tissue phosphorus content approximately 20 mg dry weight of freeze-dried algal material was finely ground, ashed at 550 °C for 24 hrs, and then eluted with a known volume of distilled water. The phosphorus content of Cladophora is given as ìgat P04—P/g dw algal material. Radiotracer determinations: In all experiments quartz jars were used to reduce adsorptive effects. The P or C of known activity was added to the seawater of predetermined phosphate content and alkalinity. The active fractions were measured at the beginning and the end of incubation. After incubation the samples were rinsed in seawater, blotted dry and freeze-dried. 5 mg sub-samples of the finely ground alga were placed in glass scintillation vials and heated in 2 ml of 30% H202 until evaporation was almost complete. This bleached and partially oxidized residue was shaken violently with scintillation fluid and activity was recorded in a Berthold Beta Liquid Scintillation Counter (Betascint BF 500). Channel settings enabled differentiation of P and C activity. Good counts for P were recorded. A high and uneven quench on C, however, necessitated the combustion of 10 mg subsamples for C determination (Packard Sample Oxidizer B 306). Adjustments have been made for combustion efficiency, quenching and alkalinity.

Crayfish Productivity, Allochthony, and Basin Morphometry

Abstract: West Lost Lake has a higher production of the crayfish, Orconectes virilis, than does nearby North Twin Lake. The basis for the higher carrying capacity of West Lost Lake lies in its steeper basin ...

The submerged aquatic macrophytes in Lake Maarsseveen I: Species composition, spatial distribution and productivity

Abstract: Little is known about the submerged vegetation of the lakes around the river Vecht area. The few reports published refer to other, shallower lakes. A study on the vegetation of the nearby Botshol by WESTHOFF (1949), repeated for submerged plants only by VROMAN (1976), reported the occurrence of several submerged angiosperm species as well as charophytes, but gave no qpantitative data. DEN H E LD et al. (1970) investigated the emergent, floating and submerged macrophytes in the De Haak lakes, applying the method of BA R KMAN et al. (1964) for vegetation analysis. WESTHO F F et al. ( 1971 ) noted the distribution of submerged macrophytes, including charophytes, in the Nieuwkoop lakes. The distribution and abundance of the submerged and floating macrophytes in Lake Maarsseveen I were studied to determine which species were present, and to assess their role in the nutrient cycles of the lake. Sampling was done with the use of SCUBA diving, which has proved useful in ecological studies on these plants (WOOD, 1963; 1975; CHAPMAN and CLAYTON, 1975; LOVE and ROBINSON, 1977; SHELDON and BOYLEN, 1978). All macrophytic species present were listed, and the seasonal changes in biomass of the predominant species were measured during the year. The plant cover was mapped out by vegetation type, and their standing crop, carbon and nitrogen content were measured. In the present study WETZE L's (1975) definition of aquatic macrophytes which includes watermosses and charophytes is used in preference to SCU LTHO RPE's (1967) definition which includes only vascular aquatic plants.

Paleolimnology of Two Shallow Lakes in Central Alberta, Canada

Abstract: An interpretation of postglacial change in water quality and productivity has been made for two shallow lakes in Central Alberta, Canada, namely Hastings Lake (longitude 113° 00′ W; latitude 53° 30′ N) and Lac Ste. Anne (longitude 114° 21′ W; latitude 53° 41′ N). Erosion rates around Lac Ste. Anne have remained constant. Similarly productivity has changed little although macrophytes contributed more to total production during the early stages. Hastings Lake has responded more sensitively to changes in the balance of precipitation and evaporation. From 5500 to 4000 year B. P. it was shallower than at present. Productivity during this early phase was less but macrophytes and allochthonous organic matter (i. e., leaf litter) probably contributed a greater proportion of the organic influx. After water levels rose productivity increased remaining steady until 2500 year B. P. when a slight decline occurred. Throughout the high water period oxygen depletion has not been serious. Any period of reducing conditions has been brief. Productivity has never been nutrient-limited. Elevation of the lake surface increased potential volume for production and reduced turbulent resuspension of bottom sediments permitting greater light penetration, and enhanced algal production. Difference between the sedimentary record of these two lakes, as well as the two basins of Hastings Lake, demonstrates the individualistic responses of basins and lakes to climatic events.

Comparative primary productivity of algal epiphytes on three species of macrophyte in the littoral zone of Lake Ohrid, Yugoslavia

Abstract: Mean total surface area available for epiphytic colonization during the study period was 1.032 m2 macrophyte surface per m2 of littoral zone for Phragmites, 0.810 m2 for Potamogeton, and 0.167 m2 for Nuphar. Seasonal rates of mean primary productivity of algal epiphytes on Phragmites from the surface to the light-compensation depth ranged from 84-1406 mg C m-2 littoral zone d-l; ranges for epiphytes on Potamogeton and Nuphar were 77-586 and 69-268 mg C m-2 littoral zone d-', respectively. Maximum rates were observed typically during June; minimum rates were observed typically during August to December. Mean daily productivity rates over the 12 month period were for epiphytes on Potamogeton 167.0, on Nuphar 100.4 and on Phragmites 671.2 mg C m-2 littoral zone d-1. Calculated annual production for epiphytes on Nuphar was 36.65, on Potamogeton 60.95 and on Phragmites 245.0 g C m-2 littoral zone yr-'. Epiphytic production data were typically considerably higher than production data obtained for littoral and pelagial planktonic algae and compare favorably with published data for epiphytic and periphytic production in Lawrence

Biomass and Productivity of a PinusPinea L. Stand.

Abstract: Among the three most frequent pine species encountered around the Mediterranean: Pinus halepensis, Pinus brutia and Pinus pinea, the last has the largest areal extent. Pinus halepensis is found mostly in the northern and western part of the Mediterranean Basin, and Pinus brutia in the eastern part. Only Pinus pinea is found all around the Basin.

Benthic Algal Productivity in a Piedmont Stream Measured by 14C and Dissolved Oxygen Change Procedures

Abstract: Estimates of benthic algal primary productivity in a stream measured by 14C incorporation and dissolved oxygen change gave similar pattern of productivity over the year. However, estimates from the 14C procedure were lower than from the D.O. change procedure. The discrepency is related in part to procedural differences but the data from experiments in which 14C uptake and D.O. change were measured simultaneously also indicated the community photosynthetic quotients were higher than those commonly used in productivity work.

The effect of dried and cracked sediment on the availability of phosphorus in a coastal lagoon

Abstract: Caimanero Lagoon (Sinaloa, Mexico) is subjected to alternate periods of low water and flooding. In the first case, more than 70% of the lagoon is dry, cracked and colonized by halophytes to a variable proportion. During the dry season, mineralization of organic matter and reavailability of phosphorus takes place to a great extent. So far, the effect of dried and cracked sediment on the reincorporation of phosphorus to the coastal lagoon ecosystem has not been evaluated. This work is the result of experiments which emulate natural conditions present during the dry season and the beginning of the flood season under the influence of tidal flux. The availability of phosphorus (orthophosphates and soluble phosphates) was significantly increased in the dry and cracked material; this phosphorus is derived from the mineralization of organic matter present in the sediment. The amount of soluble organic matter also increased during the dry season. The sedimentary drying and cracking process contributes significantly to estuarine productivity.