Rubén H. Freije

Dissolved Nutrient Availability during Winter Diatom Bloom in a Turbid and Shallow Estuary (Bahía Blanca, Argentina)

Abstract The inner zone of Bahía Blanca Estuary is a shallow, well-mixed, highly turbid, and nutrient-rich temperate ecosystem. The phytoplankton annual cycle is characterized by a recurrent winter/early-spring diatom bloom. From May to August 2002 a research program aimed to describe the potential relations between the dynamics of phytoplankton and nutrients was carried out. Phytoplankton composition, abundance, chlorophyll a (Chl a), and dissolved inorganic nutrients (nitrate, nitrite, ammonium, phosphate, and silicate) were measured. The species involved were classified in blooming (including Thalassiosira spp. and Chaetoceros spp.) and nonblooming species (including other diatoms and dinoflagellates). The results show: (1) a prebloom period, which includes low biomass values and a strong decrease of NO3−; (2) an initial bloom period characterized by high diatom abundance and Chl a, a marked dominance of Thalassiosira curviseriata, and a strong decrease of NH4+; (3) an intermediate bloom period of high abundance, codominance of blooming species, and a strong decrease of PO43−; and (4) a final bloom period with a decrease in abundance of blooming species and a general nutrient recovery. Thalassiosira curviseriata seems to be a species associated with high nutrient stock and low light intensity. Its growth, mainly concurrent with DIN decrease, was related to new production in this area. The obtained data suggest that low phosphate concentrations, more than DIN and silicates, contributed to the diatom bloom collapse. According to our results, this high production during winter can be explained as a net growth of phytoplankton because of a successful low light- and temperature-acclimated species, possibly favored by low predation and high nutrient availability.

Abundance and species composition of planktonic Ciliophora from the wastewater discharge zone in the Bahía Blanca Estuary, Argentina

The specific composition and abundance variation of the ciliate community from a wastewater discharge zone in the Bahia Blanca estuary, Argentina, were studied all throughout a year, from June 1995 to May 1996. The polluted area exhibited high values of particulate organic matter and nutrients, particularly phosphates. Aloricate ciliates were represented by 15 species belonging to the genera Strombidium Claparede & Lachmann, 1859; Strombidinopsis Kent, 1881; Cyrtostrombidium Lynn & Gilron, 1993; Strobilidium Schewiakoff, 1983; Lohmmanniella Leegaard, 1915 and Tontonia Faure-Fremiet, 1914. Tintinnids were represented by nine species belonging to the genera Tintinnidium Kent, 1881, Tintinnopsis Stein, 1867 and Codonellopsis Jorgensen, 1924. The total abundance of aloricate ciliates reached a peak of 1,800 ind. 1-1 and the total abundance of tintinnids reached a peak of 9,400 ind. 1-1. Tintinnidium balechi Barria de Cao, 1981 was the most abundant ciliate in the community. Considerations on the presence and abundance of ciliates are made in relation to physicochemical and biochemical parameters.

Factorial experimental design optimization of solid phase microextraction (SPME) conditions for analysis of butylated hydroxytoluene (BHT) in bottled water

BHT is an antioxidant utilized as additive in some foods and in packaging plastics, and its presence in bottled mineral water is possible due to its migration from bottle walls to the contents. A factorial experimental design was utilized to obtain the optimum values for the main operational parameters in the analysis of butylated hydroxytoluene (BHT) in bottled water using headspace and direct solid-phase microextraction (SPME) in the pre-concentration step. The parameters optimized were sample pH, temperature and ionic strength. The separation, detection and quantitation of the extracts were performed by gas chromatography coupled to mass spectrometry. Preliminary experiments were made to select the best fiber for the extraction procedure. Polydimethylsiloxane (PDMS) fibers were selected, and the optimized methodology was successfully applied to the extraction and quantitation of BHT in real samples of mineral and mineralized bottled water.

Mercury distribution in estuarine environments from Argentina: the detoxification and recovery of salt marshes after 15 years

Total Hg contents from abiotic (surface sediments and suspendedparticulate matter) and biological (crabs, fishes and halophytes)compartments from Bahía Blanca estuary and Mar Chiquita CoastalLagoon, Argentina, have been monitored since the 1980s. At BahíaBlanca estuary, high Hg concentrations were recorded during the early1980s in surface sediments (0.34 ± 0.22 μg/g) andsuspended particulate matter (0.19 ± 0.10 μg/g). Fishspecies, Mustelus schmitti (0.89 ± 0.29 μg/g), Paralichthys brasiliensis (0.85 ± 0.18 μg/g) and Micropogonias furnieri (0.37 ± 0.11 μg/g) also presentedhigh Hg concentrations. The large industrial nucleus located within theestuary has been identified as the main metal source for this environment.Hg contents from the same area during 1996–1998 were significantlylower: surface sediments (0.164 ± 0.023 μg/g), suspendedparticulate matter (0.048 ± 0.0017 μg/g), fish Micropogonias furnieri (0.13 ± 0.02 μg/g) and crab Chasmagnathus granulata (0.334 ± 0.071 μg/g). This trendof environmental detoxification is probably related with (i) thetechnological changes incorporated by the local industry, (ii) a mostadequate management of industrial effluents, and (iii) the removal ofgreat sediment volume by dredging and refill.During the 1980s Mar Chiquita Lagoon Hg concentrations reached 0.08± 0.01 μg/g in surface sediments and 0.09 ±0.025 μg/g in suspended particulate matter, and 0.14 ±0.04 μg/g in the fish Basilichthys bonariensis and 0.22 ±0.08 μg/g in Paralichthys brasiliensis, and 0.08 ±0.01 μg/g in the crab C. granulata, Hg concentrations werelower than at Bahía Blanca. Remote Hg sources for this Coastal Lagoonand atmospheric and stream transport of Hg is proposed as major Hgsources, since no Hg point sources exists nearby. Mercury concentrationsrecorded in the 1996–1998 period were lower than those recorded inthe previous decade: surface sediments (0.019 ± 0.004 μg/g), suspended particulate matter (0.030 ± 0.008 μg/g), halophyte Spartina densiflora (0.013 ± 0.008 μg/g) or crab C. granulata (0.011 ± 0.009 μg/g).Both Hg bioaccumulation and biomagnification processes were verified inBahía Blanca estuary and in Mar Chiquita Coastal Lagoon. This apparentrecovery of both estuarine environments deserves to be carefully analyzed,in order to fully understand the foundations of these processes.

Phytoplankton dynamic in mar chiquita coastal lagoon (Argentina), and its relationship with potential nutrient sources

Abstract The concentration and distribution of nutrients (nitrate, nitrite, phosphate, silicate) in water, photosynthetic pigments (chlorophyll a and phaeopigments) in suspended particulate matter (SPM), and phytoplankton from Mar Chiquita Coastal Lagoon, in Argentina, was studied along six (6) sampling stations during a year in order to know their spatial and temporal variations. Internationally standardized analytical methods were applied in order to reach these objectives. The use of soils for farming and continental runoff of the adjacent terrestrial systems close to the coastal lagoon seemed to be a significant nutrient source for this water body, which is able to support its own dynamic of phytoplankton within this water body. Results obtained regarding nutrient and pigment distribution allowed the identification of two different systems within the coastal lagoon: one under marine influence and the other under inland influence, with different ecological and environmental characteristics. Temporal trends of the corresponding phytoplankton development have been identified, and it has been observed that the biological production which occurred within the coastal lagoon along the whole year was higher than corresponding ones from other coastal environments in Argentina. Moreover, nutrient occurrence within the internal region favored the development of the highest biomass detected within the whole lagoon. The system seems to function as a transition zone, which profits from unusual nutrient inputs, together with other environmental conditions (salinity, temperature), bringing continuous nutrient availability for phytoplankton and consequently food supply for marine and estuarine organisms.

Phenological Changes of Blooming Diatoms Promoted by Compound Bottom-Up and Top-Down Controls

Understanding phytoplankton species-specific responses to multiple biotic and abiotic stressors is fundamental to assess phenological and structural shifts at the community level. Here, we present the case of Thalassiosira curviseriata, a winter-blooming diatom in the Bahía Blanca Estuary, Argentina, which displayed a noticeable decrease in the past decade along with conspicuous changes in phenology. We compiled interannual field data to assess compound effects of environmental variations and grazing by the invasive copepod Eurytemora americana. The two species displayed opposite trends over the period examined. The diatom decreased toward the last years, mainly during the winters, and remained relatively constant over the other seasons, while the copepod increased toward the last years, with an occurrence restricted to winter and early spring. A quantitative assessment by structural equation modeling unveiled that the observed long-term trend of T. curviseriata resulted from the synergistic effects of environmental changes driven by water temperature, salinity, and grazing. These results suggest that the shift in the abundance distribution of T. curviseriata toward higher annual ranges of temperature and salinity—as displayed by habitat association curves—constitutes a functional response to avoid seasonal overlapping with its predator in late winters. The observed changes in the timing and abundance of the blooming species resulted in conspicuous shifts in primary production pulses. Our results provide insights on mechanistic processes shaping the phenology and structure of phytoplankton blooms.