Microbial mats associated with bryozoans (Coorong Lagoon, South Australia)

Summary Bryostromatolites are laminated carbonate rocks composed of bryozoan zoarial laminae. The laminated texture is frequently caused by patterns of bryozoan self overgrowth as a regular defensive tactic against microbial fouling. In the Coorong Lagoon (South Australia), another type of bryostromatolite is present where the laminated growth of the weakly calcifying bryozoan speciesConopeum aciculata is postmortally stabilized by cyanobacterial mats at the surface, and fungal mats settling in the zooecial cavities. A tough extracellular slime network produced by benthic cyanobacteria is a trap for sediment particles, provides a method of adhesion to the bryozoan substrate, and produces a biological lamination by the vertical stratification of dead bryozoan skeletons. These slimes are also important for the preservation of cell structures and for their fossilization. Seasonal fluctuations in salinity and water level are the most important regional control factors, causing a phase displacement in the growth optima of microbial mats and bryozoans, thereby resulting in a rigid bryostromatolitic fabric.     

Seasonal Variation of the Macrozoobenthic Community Structure at Low Salinities in a Mediterranean Lagoon (Monolimni Lagoon,Northern Aegean)

The macrozoobenthic community structure and dynamics at low salinities (0.3–6 psu) in a Mediterranean lagoon (Monolimni lagoon) were investigated. Samples were collected monthly from February 1998 to February 1999 at two sampling stations. Community structure was analyzed by means of uni‐ and multivariate methods. 21 taxa were collected; the amphipod Corophium orientale and the gastropod Ventrosia maritima dominated the assemblages. Total abundance peaked (50,000–60,000 individuals m^–2) in mid or late autumn. Community structure showed an almost even seasonal periodicity; seasonal changes were mainly derived from the intense variation in abundance of most species and the non–occurrence of a few ones (e.g. Corophium insidiosum, Polydora ciliata) in spring and summer. Non– occurrence, which led to a depression of the most diversity indices, was possibly the only direct impact of the extremely low salinities (~0.3 psu) on community structure. The main structuring factors of the community in the deeper outer part of the lagoon were water temperature and depth, and in the innermost part, where a Ruppia maritima meadow occurred, were water temperature and predation pressure by crabs (Carcinus aestuarii) and gobies (Knipowitchia caucasica). A temporary decline in total abundance in summer followed an increase in abundance of these predators. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Helminth parasites of Clarias gariepinus (Clariidae) in Lekki Lagoon, Lagos, Nigeria

A total of 360 randomly selected specimens of Clarias gariepinus (Clariidae) recovered from Lekki Lagoon were examined for intestinal helminth parasites. Parasite prevalence and worm burden were low; 17 (4.72%) of the specimens examined were infected with gastrointestinal helminths. The helminth worms recovered include, three cestodes Polyonchobothrium clarias, Stocksia pujehuni and Wenyonia acuminata and a nematode, Paracamallanus cyathopharynx. There was no statistically significant difference in the infection of the male and female Clarias gariepinus; the infection rates in male and female samples were 5.75% and 3.76% respectively. Parasite prevalence was related to the length and weight of the specimens. The fish samples were observed to show negative allometric growth and smaller samples recorded higher helminth infection.     

Bottom Communities of Semyachik Lagoon (Kronotskii Biosphere Reserve, Eastern Kamchatka)

Bottom communities of Potamogeton filiformis,Zostera marina+ Z. japonica+ Macoma balthica, Enteromorpha prolifera, and a stony block–boulder intertidal community were distinguished in Semyachik Lagoon. The macrobenthos associated with these communities is described. Generally, the biomass and occurrence frequency indices of the macrozoobenthic communities of the lagoon are an order of magnitude lower than those of macrophytobenthic communities (Kafanov, Plekhov, 1998); therefore, they do not play a significant role in bottom community structure. With the exception of the stony block–boulder intertidal community, their spatial distribution is entirely determined by the distribution of underwater vegetation, which is completely controlled by the geomorphological and hydrological features of the lagoon.     

Bottom Communities of Nyivo Lagoon (Northeastern Sakhalin)

Clasterization of benthic stations by biomass of common species using an index of coenotic similarities allowed us to distinguish three communities of macrophytobenthos (Zostera marina + Z. japonica, Zostera japonica, and Potamogeton pectinatus) and eight macrozoobenthos communities (Macoma balthica, Limnodrilus hoffmeisteri + Anisogammarus tiuschovi, Spio filicornis + Archaeomysis grebnitzkii, Kamaka kuthae, Glyptotendipes paripes, Neomysis awatschensis + Dolielinotus moskvitini, Neomysis mirabilis, and Anisogammarus tiuschovi + Littorina sitkana + Crangon septemspinosa). The bulk of the bottom surface is occupied by a community of Zostera marina + Macoma balthica with the mean biomass of the dominating species reaching 0.3–1386.6 and 573.9 g/m², respectively. Specific geomorphologic and hydrologic features, as well as the presence of many estuarine areas in Nyivo Lagoon, provide conditions for numerous different fresh-and brackish water communities and variations of them. However, bottom communities cannot be clearly separated into mostly freshwater and mostly brackish communities, which is the case for Pil'tun Lagoon, a well studied lagoon in eastern Sakhalin. Several decades of timber rafting in the Tym' River has had a significant effect on bottom biota and the communities of Nyivo Lagoon. Considering the well-known negative effects of phenol and its derivatives on benthic biota and communities derived during timber decomposition, the sources of pollution of the natural environment in the lagoons of eastern Sakhalin must be evaluated and differentiated.     

Population Dynamics,Reproductive Biology and Productivity of Streblospio shrubsolii (Polychaeta: Spionidae) in Different Sediments at Low Salinities in a Mediterranean Lagoon (Monolimni Lagoon,Northern Aegean)

Monthly samples of Streblospio shrubsolii were collected from February 1998 to February 1999 at both parts of Monolimni Lagoon (0.3 psu < Sal. < 6 psu). Streblospio shrubsolii displayed a life cycle of about one year. Reproductive activity occurred from February to October. The worms showed a mean of 14 or 16 gametogenic segments. Reproductive activity, growth and density increased during spring despite the low salinities (∼0.3 psu). Streblospio shrubsolii showed faster growth, larger body size during autumn–winter, more reproductive peaks, a relatively higher mean annual density, mean anual biomass (B) and annual production (P) at the innermost part of the lagoon, in organically richer very fine sand, than those at the outer part in fine sand. Mean annual density was 1,320 individuals m^–2 at the outer part and 1,745 individuals m^–2 at the innermost. Production calculated by Hynes' s method gave a B of 0.20 g DW m^–2 y^–1 and P of 0.45 g DW m^–2 y^–1 at the outer part; the respective values at the innermost part were 0.29 g DW m^–2 y^–1 and 0.61 g DW m^–2 y^–1. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Seahorse (Hippocampinae) population fluctuations in the Ria Formosa Lagoon,south Portugal

Comparisons of three sets of surveys in the Ria Formosa Lagoon, Portugal, over a 13 year period (2001–2002, 2008–2009 and 2010–2013) revealed significant population fluctuations in at least one of the two seahorse (Hippocampinae) species living there, and that those fluctuations were potentially associated with habitat changes in the lagoon. After a significant decline between the first two survey periods (2001–2002 v. 2008–2009), long‐snouted seahorse Hippocampus guttulatus populations increased significantly between 2008–2009 surveys and new 2010–2013 surveys. There were no significant differences in H. guttulatus populations between the 2001–2002 and 2010–2013 surveys. In contrast, there were no significant differences in short‐snouted seahorse Hippocampus hippocampus densities among the 16 sites surveyed throughout the three sampling periods, although the ability to detect any change was hampered by the low densities of this species in all time periods. Fluctuations in H. guttulatus densities were positively correlated with the percentage of holdfast coverage, but with none of the other environmental variables tested. These results highlight the importance of holdfast availability in maintaining stable seahorse populations. While population fluctuations are certainly more promising than a consistent downward decline, such extreme fluctuations observed for seahorses in the Ria Formosa Lagoon could still leave these two species vulnerable to any additional stressors, particularly during low density periods.     

Multiannual Chattonella subsalsa Biecheler (Raphidophyceae) blooms in a Mediterranean lagoon (Santa Giusta Lagoon,Sardinia Island,Italy)

Recurrent blooms of Chattonella subsalsa (Raphidophyceae) were associated with fish kills in Santa Giusta Lagoon (Mediterranean Sea). This study investigated the population dynamics of C. subsalsa and its relationship with environmental and meteorological conditions, using multiannual ecological data (1990–2016). In addition, for the first time, this study examined the presence of C. subsalsa cysts in lagoon sediments. The species was first detected in Santa Giusta Lagoon in July 1994. Bloom events coinciding with fish kills were recorded in 1994, 1998, 1999, and 2010. The timing and dynamics of C. subsalsa blooms and fish kills varied over the examined period. Presence of C. subsalsa was strongly influenced by temperature, especially in the early years of the series (1990–2002). Temperature control may have been lesser important in the more recent years, when higher temperature may have generated continuative suitable conditions for C. subsalsa affirmation, especially in July. Thus, the variations in the availability of food (via autotrophy and/or mixotrophy) could be one of the control keys on the proliferation of this species in the future in SG. Cysts of C. subsalsa were present in lagoon sediments at abundances ranging 200–2000 cysts g⁻¹ wet sediment. This study is among a few that have examined C. subsalsa population dynamics and bloom events in the field over a long time period. Findings from this study contribute to a better understanding of C. subsalsa bloom development, by identifying environmental and meteorological variables that may promote blooms of this species in the Santa Giusta Lagoon.     

Macrozoobenthic community structure in a poikilohaline Mediterranean lagoon (Laki Lagoon, northern Aegean)

The community structure of the macrobenthic fauna was studied in the overall area of Laki Lagoon in September 1997 (salinity 32–35 psu) and monthly from February 1998 to February 1999 in the innermost part of the lagoon (salinity 0.1–6.8 psu). Community structure was analyzed by means of uni- and multivariate methods. In September 1997, the macrofauna in the outer part of the lagoon was characterized by a higher diversity and the occurrence of both lagoonal and marine species, and in the innermost part by a higher total abundance and the occurrence of a few lagoonal species. The combination of distance from the sea, depth, salinity and sediment organic matter correlated best with the spatial distribution pattern of the macrobenthic fauna. Community structure in the innermost part of the lagoon showed a seasonal periodicity. Species composition during spring 1998, at 0.1–2.0 psu, was similar to that in September 1997. During summer the macrobenthic fauna became impoverished, but recovered from late summer onwards. The salinity increase during summer (up to 5–7 psu) was followed by the appearance of marine species in the innermost part of the lagoon. Total abundance displayed a peak in late spring and a lower one in mid-autumn. The seasonal dynamics of the faunal assemblage was mainly governed by water temperature. Predation pressure by Atherina boyeri may have contributed to quantitative community changes during autumn.     

Benthic Primary Production Budget of a Caribbean Reef Lagoon (Puerto Morelos,Mexico)

High photosynthetic benthic primary production (P) represents a key ecosystem service provided by tropical coral reef systems. However, benthic P budgets of specific ecosystem compartments such as macrophyte-dominated reef lagoons are still scarce. To address this, we quantified individual and lagoon-wide net (P_n) and gross (P_g) primary production by all dominant functional groups of benthic primary producers in a typical macrophyte-dominated Caribbean reef lagoon near Puerto Morelos (Mexico) via measurement of O₂ fluxes in incubation experiments. The photosynthetically active 3D lagoon surface area was quantified using conversion factors to allow extrapolation to lagoon-wide P budgets. Findings revealed that lagoon 2D benthic cover was primarily composed of sand-associated microphytobenthos (40%), seagrasses (29%) and macroalgae (27%), while seagrasses dominated the lagoon 3D surface area (84%). Individual P_g was highest for macroalgae and scleractinian corals (87 and 86 mmol O₂ m⁻² specimen area d⁻¹, respectively), however seagrasses contributed highest (59%) to the lagoon-wide P_g. Macroalgae exhibited highest individual P_n rates, but seagrasses generated the largest fraction (51%) of lagoon-wide P_n. Individual R was highest for scleractinian corals and macroalgae, whereas seagrasses again provided the major lagoon-wide share (68%). These findings characterise the investigated lagoon as a net autotrophic coral reef ecosystem compartment revealing similar P compared to other macrophyte-dominated coastal environments such as seagrass meadows and macroalgae beds. Further, high lagoon-wide P (P_g: 488 and P_n: 181 mmol O₂ m⁻² lagoon area d⁻¹) and overall P_g:R (1.6) indicate substantial benthic excess production within the Puerto Morelos reef lagoon and suggest the export of newly synthesised organic matter to surrounding ecosystems.     

Organic Matter,Carbon, Nitrogen and Phosphorus Contents of the Mesozooplankton,Mainly Acartia clausi,in a Tropical Brackish Lagoon (Ebrié Lagoon,Ivory Coast)

Mesozooplankton samples were collected over a period of one year in five stations of the Ebrié lagoon and analysed for organic, carbon, nitrogen and phosphorus contents. When zooplankton was dominated by A. clausi, body composition was relatively stable compared with the broad variability of environmental factors (mainly salinity, food abundance and composition), although a negative hypothetic influence of salinity may have occurred. Body composition was comparable when zooplankton was dominated by Pseudodiaptomus hessei and freshwater species, but contents were significantly lower for assemblages dominated by more exclusively marine species (Paracalanus spp., Oithona spp., marine cladocerans, chaetognates, etc.).     

Annual Cycles and Budget of Nutrients in Berre Lagoon (Mediterranean Sea,France)

The annual cycles of nutrients in the Etang de Berre were studied in 1985. From measurements twice a month at the input points, daily data for the freshwater flow and from daily measurements at the output point, an estimation is proposed for a nutrient budget. Seasonal variability is important, and a biological control of nutrient availability (locally remineralized products) results in a hydrologically controlled system (nutrients carried by continental waters) which produces the very high microalgal biomass observed in the lagoon. The seasonal halocline brings the euphotic layer very close to the remineralization site: nutrients are then constantly available to the phytoplankton.     

Population studies on the Amphipoda of Mazoma Lagoon (Greece)

The life cycles of four amphipod species—Gammarus insensibilis, Dexamine spinosa, Microdeutopus gryllotalpa andCorophium insidiosum—were studied in the brackish-water lagoon Mazoma of the Amvrakikos Gulf, Ionian Sea.G. insensibilis has an annual life cycle with limited recruitment over the year and maximum reproductive activity in the winter months.D. spinosa exhibits continuous recruitment in the lagoon with a maximum in summer. Both species produce a single brood per female per yer. Continuous recruitment was observed during the summer months forM. gryllotalpa andC. insidiosum, and multiple breeding per female per year. Sex ratios varied considerably over the year, with a persisting preponderance of the females.     

Vegetation structure and ecology of the Cufada Lagoon (Guinea-Bissau)

The Cufada Lagoon, in the southern part of Guinea‐Bissau, West Africa, is a shallow lagoon with a surface area of 190 ha in the rainy season. The vascular flora and physico‐chemical characteristics of the lagoon were studied in December 1997 (end of the wet season) and May 1998 (dry season). The lagoon water is soft, with acid pH, low conductivity and low transparency. The maximum depth is 2.25 m in the rainy season and 1.20 m in the dry season. A total of 46 vascular plant species were recorded, 32 being emergent macrophytes, mostly Gramineae and Cyperaceae, five floating‐leaved, three submerged, one surface‐floating and also five shrubs. Cluster analysis of the floristic data shows two main groups of inventories in both seasons, grouping almost nine‐tenths of the vegetation samples. The inventories in these groups correspond to two main vegetation types and can be spatially arranged. In the deepest inner part of the lagoon, Nymphaea lotus is the most important species, while Oryza longistaminata dominates in the shallower part. In spite of the shallow depth, the middle of the lagoon remains uncolonized by macrophytes. The main factors limiting the colonization by plants of the lagoon seem to be the low mineral and nutrient content of the water and its low transparency.     

Supratidal foraminifera as ecological indicators in anthropically modified wetlands (Lagoon of Venice, Italy)

In transitional environments, the intertidal zones represent a peculiar case characterized by halophile vegetation and by a low diversity benthic community. On these areas just a few particular foraminiferal species, a class of Protoctista secreting a shell called test, can survive for a certain time out of water. They are distributed in well-defined vertical zonations with respect to mean sea level and they correspond to analogous marsh floral zonations. In particular, the Trochammina macrescens Brady + Trochammina inflata (Montagu) association characterizes the salt marsh zone above mean high water level. The potential of these taxa as bioindicators is tested, since their presence-absence-dominance differentiates the subtidal/supratidal environments. Over the last few centuries, various engineering works generated major physical changes in the Venetian Lagoon. These changes affected the natural evolution of the intertidal morphologies, the surface of which is decreasing. In an attempt to reverse this tendency, numerous artificial salt marshes have been constructed and more are under construction. In this study, the Mazzorbo artificial salt marsh, built during the second half of 1999, is considered. On its surface, 16 samples were collected along a transect line in May 2008 to verify the ecological role of this salting within the lagoon ecosystem. The sediment grain size distribution of the salt marsh reflects the dissipative role of the tide and the effect of sediment transport due to the wave and tidal action. However, the presence of only a few Trochammina individuals shows that the foraminiferal fauna did not recognise this morphology as a salt marsh. The lack of Trochammina colonisation can be related to the excessive elevation of the salt marsh surface. This hypothesis is confirmed by the lack of the salt-tolerant plant Spartina. The unsuccessful colonisation by the foraminifera seems to indicate that this artificial salting does not have the natural dynamism of the intertidal morphologies and it may only be classified as land recovery. The supratidal foraminiferal taxa can act as an ecological indicator: through their observation it is possible to verify whether an artificial salt marsh accomplishes its task of functioning as an ecological unit with the community of organisms.     

Movements and home range of ferrets (Mustela furo) at Pukepuke Lagoon,New Zealand

Abstract

Ferrets at Pukepuke Lagoon were live-trapped during the periods November 1970 to August 1973 and January 1976 to July 1977. Although the sex ratio of the 75 trapped ferrets was equal, there was a strong bias towards male captures in the earlier period (58.4%) and towards female captures in the later period (68.7%). Habitat modification and changes in the trapping programme for the later period probably resulted in the increased abundance and capture rate of females. Between consecutive captures 58.2% of male movements exceeded 250 m, as against on1y 39.7% of female movements; the mean distance between consecutive captures was 435 m for males and 285 m for females. Mean monthly movements varied from 700 m in January to 315 m in June for males, and from 360 m in March to 150 m in September for females. Juveniles of both sexes moved similar, intermediate distances. Dispersing juveniles were trapped from January until April; males tended to appear in traps earlier in the year than females. Only 4 of 14 juvenile males setNed as residents, hut 15 of 28 juvenile females did so. Male and female home ranges overlapped extensively, but within each sex individual ranges were usually separate. Resident males maintained a well defined spacing pattern, adjusting their boundaries if a juvenile settled or a neighbouring range became vacant. In 1976 six females had overlapping ranges in an area of albundant food. Female ranges (12.4 ha) were on average smaller than male ranges (31.3 ha); home ranges of both sexes were smaller during the breeding season (August-February) than at other times.     

Analysis of fish parasitofauna in Vistula Lagoon (the Baltic Sea)

The characteristics of parasitofauna (81 species) of 15 fish species from Vistula Lagoon (the Baltic Sea) are given. Parasites with a direct developmental cycle dominate. Parasites with a complicated developmental cycle are represented mainly by species developed through zoobenthos. Some of the parasites testify to the deterioration of the ecological state of the lagoon. A zoogeographic analysis of fish parasitofauna has shown the presence of five faunistic complexes. In Vistula Lagoon freshwater species dominate, but marine species are also recorded. Species that appeared in the lagoon as a result of human commercial activity are also registered.     

Distribution, reproduction and growth of the catfish, Chrysichthys walkeri (Gunther) in the Lekki Lagoon, Nigeria

An investigation was made on the biology of the catfish, Chrysichthys walkeri (Gunther) occurring in the Lekki Lagoon. The catfish was evenly distributed over the six sampled stations of the lagoon with the sites of the shallow water stations probably serving both as breeding and nursery grounds.
Fecundity estimates for this species ranged from 896 to 4168 eggs. The average number of eggs per female was 2084. Laboratory incubated eggs hatched after 3 days with the yolk sac being completely absorbed on the seventh day. The fry averaged 8.6 mm on their first day of life.
The catfish attained a maximum total length of 25.7 cm within a period of 2 years. There were no significant differences in the growth pattern of this species during the dry and rainy seasons.     

Diel dynamics of net phytoplankton in Semyachik Lagoon (Kronotskii Bay, Kamchatka) in August 1982

At three stations in the shallow Semyachik Lagoon, Kronotskii Bay, Kamchatka, 72 species and intraspecific taxa of microalgae were found. Diatoms (55) were the dominant group. In the qualitative and quantitative respects, phytoplankton was mainly represented by casually planktonic (benthic) species of diatoms. The general features of diel dynamics of phytoplankton were similar at the three stations and depended on the fluctuations of the level of tidal currents. The highest biomass (up to 363 mg/m³) and density (up to 66000 cells/I) were observed between 12∶00 and 18∶00 at low tide; these characteristics were an order of magnitude lower than at high tide.