Low Biotic Diversity Research Articles

Trophic interactions and food web structure of aquatic macroinvertebrate communities in afromontane wetlands: the influence of hydroperiod

Hydroperiod is considered an important aspect in shaping community structure and ecosystem patterns in temporary wetlands. However, most studies have focused on the community structure, demonstrating that biotic diversity increases with hydroperiod. Theory suggests that ecosystem patterns like trophic interactions and food web structure will also respond to hydroperiod in the same way. However, there are limited studies exploring ecosystem structure and patterns to changing hydroperiod in temporary wetlands. Maloti-Drakensberg Mountain region of southern Africa has a series of rock pools (shorter hydroperiod) and tarns (longer hydroperiod) that allowed us to explore the effect of hydroperiod on aquatic biodiversity and trophic interactions using stable isotope techniques. We hypothesised that tarns will have higher biotic diversity and complex food web structure as compared to rock pools, which we expected to exhibit low biotic diversity and simple food web structure. Our results were in agreement with our hypothesis, where tarns were characterised by longer food chain length, higher trophic level diversity, greater trophic divergence and even species distribution in the isotopic space. Thus, demonstrating a well-developed and complex food web structure. In contrary, rock pools were characterised by shorter food chain length, small trophic diversity with trophic redundancies and species clustering. Thus, representing a simple and a poorly developed food web structure. Further, macroinvertebrate biotic diversity was significantly higher in longer hydroperiods, also longer hydroperiod exhibited less dramatic changes in the physicochemistry characteristics, representing a more stable environment than shorter hydroperiods. This study demonstrates that hydroperiod not only affects aquatic biological diversity but ecosystem structure, as well.

Diverse preserved dinosaur footprint assemblage from Jurassic–Cretaceous transition eolian dune deposits of western Shandong Province, China

Ancient desert, characterized by low biotic diversity as well as low preservation potential, has long been assumed as devoid of biotic activity. However, recent works from Mesozoic trace fossils preserved in the eolianites in North America, South America and East Asia indicate that the ancient desert can also have diverse inhabitants. This paper presents a diversified preserved dinosaur track assemblage from the Jurassic-Cretaceous transition eolian dune deposits in western Shandong Province, China. Based on the ichnological analysis, tracks are assigned to ichnogenus Anomoepus, Eubrontes-like and Ornithopodichnus-like forms, representing the oldest and second example of the Chelichnus ichnofacies reported from China as well as Asia. Sedimentological analysis of the tracksites indicates that tracks occurred in linear dunes under arid climatic conditions. Well-preserved tracks with detailed anatomical information are more likely to be preserved in moist sands, contrary to the dry cohesionless sands. Anomoepus and Ornithopodichnus-like tracks cooccurring with northwestward winds were made during summer wet season, while Eubrontes-like track was present during winter dry season characterized by strong northeastward wind, implying different habits between ornithopod and theropod dinosaurs. The preserved Jurassic-Cretaceous transition dinosaur tracks in eolian dune deposits not only expand the spatial-temporal distribution of dinosaur fauna in North China, but also greatly improve our understanding of the adaptive capacity of dinosaurs in severe living conditions, such as the desert environment.

Spatial Fluctuations in Zooplankton Biotypes of the Imo River in a Niger Delta Area of Nigeria

<b> </b><b> </b>The study identified zooplankton biotypes of the increasingly in-stream sand-mined Imo River in Etche, a Delta area of Nigeria, as indicators of the health of the aquatic ecosystem. Plankton samples were collected with a 55μm mesh size plankton net that was hauled horizontally along the river course for 5 minutes at 7 sampling locations once monthly for 24 months (March 2007-February 2009). Samples were fixed/preserved in 4% formalin solution in labelled plastic containers. In the laboratory, a wide-mouthed pipette was used to withdraw 1ml of the plankton subsample and to place it on a Sedge-wick rafter-counting chamber. Standard keys were used for species identifications and counts made through direct microscopy. The ANOVA, post-hoc plots of group means, hierarchical cluster analysis (HCA), and the Margalef’s species diversity index were used to analyze data. Zooplankton had low diversity index (0.926 ± 0.100) and was made up of 7 taxa and a mean density of 433 organisms/ml; with order of dominance as Cladocera (25.87%)> Copepoda (20.55%)> Protozoans (19.17%)> Rotifera (18.71%)> fish eggs and larvae (9.24%)> Crab larvae (4.62%)> Beetle larvae (0.69%). Plankton abundance peaked in sampling location 1 (140 organisms/ml; 32.41%) and was least in location 3 (21 organisms/ml; 4.86%), even as there was marked spatial heterogeneity in the taxa composition[F<SUB>(11.94)</SUB>>F<SUB>crit(3.94)</SUB>] at P<0.05. The HCA revealed that crab larvae, fish eggs and larvae, beetle larvae, and copepods formed the first and richest cluster, while the rotifers, cladocerans and protozoans formed the sparse 2<SUP>nd</SUP>, 3<SUP>rd</SUP> and 4<SUP>th</SUP> clusters, respectively. The low biotic diversity recorded could be attributed to growth-limiting perturbations created by ongoing in-stream sand mining in water columns.

Do channel restoration structures promote ammonium uptake and improve macroinvertebrate-based water quality classification in urban streams?

Comparisons of ammonium uptake parameters in restored and unrestored urban streams suggest that sufficient light penetration to areas where hard substrates have been installed should be an important management consideration to enhance biofilm accumulation and subsequent ammonium removal to the streambed. We studied ammonium uptake parameters and macroinvertebrate communities in 3 types of restoration structures (riffle, cross vane, and step pool) in restored streams and in unrestored urban streams in Greensboro, North Carolina, USA, where urbanization has led to high nutrient concentrations, degraded channel conditions, and low biotic diversity in streams. Restored streams had a significantly higher percentage of large substrates (boulder, cobble, and gravel) and less canopy cover compared to unrestored streams (P = 0.029; t-test), providing substrates and sufficient light penetration for biofilm growth. Benthic chlorophyll a was higher in restored compared to unrestored streams. Significantly shorter ammonium uptake length (P = 0.02) was observed in restored compared to unrestored sites. This effect was probably related to greater biofilm development and therefore more assimilation sites for removal of ammonium from the stream water. Differences in uptake velocity (P < 0.07) and areal uptake (P < 0.06) were not significant. Despite the shorter ammonium uptake length in restored streams, there was little improvement in measures of macroinvertebrate-based water quality classifications between restored and unrestored streams (P = 0.545). Because this study was completed 2 years postrestoration, continued, longer-term monitoring of restored streams is needed for full evaluation of the effects of the restoration approaches used in these streams.

Early Jurassic benthic foraminiferal diversification and biozones in shallow-marine carbonates of western Tethys

Low-latitude carbonate platforms dominated the southern and northern margins and microplates of western Tethys during the Early Jurassic. However, these have proved difficult to date in the past partly due to a lack of study but also a perception of low biotic diversity following the Triassic-Jurassic extinction event. Detailed logging and sampling of seven continuously exposed sections of Lower Jurassic shallow-marine carbonates in Gibraltar, Morocco, Tunisia, Greece, Italy, and in Spain reveals the occurrence of 12 benthic foraminifera species. These taxa are described and illustrated, and include: one new speciesTextulariopsis sinemurensis, new records for the Early Jurassic, and new records for this region. Five new biozones for the late Hettangian to early Pliensbachian time interval are erected from the consecutive appearance of benthic foraminifera within these sections, from top to base:Lituosepta compressa, Lituosepta recoarensis, Everticyclammina praevirguliana, Siphovalvulina colomi andSiphovalvulina gibraltarensis. This has enabled the correlation of these sections for the first time from the northern and southern Tethys margins and from the Apuleian and Pelagonian microplates within Tethys. The foraminiferal occurrences indicate a similarity of associations from the southern and northern shallow carbonate shelves of Tethys, whilst reflecting the relative isolation of the Apuleian and Pelagonian microplates within Tethys. The foraminifera show a progressive diversification of forms through the late Hettangian to early Pliensbachian interval that is interpreted to reflect the evolutionary recovery and diversification of these biotas following the Triassic-Jurassic extinction event.

PALEOECOLOGY OF GIANT INOCERAMIDAE (PLATYCERAMUS) ON A SANTONIAN (CRETACEOUS) SEAFLOOR IN COLORADO

Giant Middle Coniacian to Lower Campanian Platyceramus Seitz is among the largest Cretaceous bivalves, commonly reaching an axial length of over 1 m, and occasionally over 2–3 m in size. The genus is characterized by its large size, very low convexity, normal inflation limited mostly to the umbonal area, and flattened flanks. It is especially common in moderately deep calcareous shale facies, as well as in chalks and limestones of the Niobrara Formation and equivalents. Preferred facies contain abundant pyrite, elevated total organic carbon (TOC), and very low biotic diversity. The genus maintains its giant size in these facies, and becomes more abundant. It clearly prefers dysoxic facies. As such, it probably is chemosymbiotic; photosymbiosis is almost ruled out because of inferred water depths of 200–350 m. It is also found more sparsely, and of smaller size, in oxygenated facies, including shoreface sandstone. The study area contains over 81 giant-sized Platyceramus platinus (Logan, 1898) on a single bedding plane; there are very few small ones. This allows spacing, orientation, and size analysis to be performed on an adult population.

The impact of the Cyanamid Canada Co. discharges to benthic invertebrates in the Welland River in Niagara falls, Canada

: In 1986, the International Joint Commission (IJC) recommended that the Niagara River watershed should be declared an Area of Concern (AOC). This IJC recommendation was ratified by the 4 signatories of the Great Lakes Water Quality Agreement. In order to delist an AOC, it is necessary to locate any areas of impairment within the watershed and carry out remediation projects that permit uses that were previously impaired. To this end we attempted to determine whether or not the sediments at 7 study sites near the Cyanamid Canada (Chemical) Co. were contaminated at levels that would result in the impairment of the natural biota which inhabit the watershed.The Cyanamid Canada (Chemical) Co. discharges ammonia wastes, cyanide, arsenic and a variety of heavy metals into treatment systems which ultimately discharge to the Welland River, the major Canadian tributary to the Niagara River. This portion of the Welland River near the factory was designated a Provincially significant (Class one) wetlands by the Ontario Ministry of Natural Resources. In 1986, the mean discharge to a creek from Cyanamid Canada Co. was 27,342 m(3) per day (MOE, 1987). Similar discharge volumes occurred in 1989. In 1991, the total discharge was 25,000 m(3) per day (MOE, 1991).The majority of the benthic invertebrates collected from the study area were pollution tolerant taxa (e.g., sludge worms constituted 68% of all the organisms collected). The lowest chironomid densities were observed at stations 1, 2, and 4, which were the only stations situated close to Cyanamid's discharge pipes. The absence, of clams and mayflies which burrow to greater depths than do chironomids and sludge worms, probably reflects the inability of the deeper dwelling burrowers to tolerate the contaminants which we recorded at these 3 stations. The absence of all crustaceans from these same 3 stations (stations 1, 2 and 4) when coupled with their low biotic diversity and the elevated heavy metal concentrations in the sediments were cause for concern. In addition, stations 2 and 4 displayed the highest frequency of chironomid mentum deformities.Stations 1 and 2 were located near a pipe which was one of Cyanamid Canada Company's major discharge point sources to the Welland River until a court order in 1980 stopped the company from discharging toxic material to the Welland River via that pipe. Elevated levels of cobalt (10 times above background), molybdenum (6 times above background), nickel (8 times above back-ground), tungsten (284 times above background) and zinc (20 times above background) near the abandoned discharge pipe were correlated with the presence of pollution tolerant chironomid taxa such as Polypedilum and Procladius. The highest sludge worm densities were also observed at the abandoned pipe site which was the only site where oily wastes were found in the sediments.Among the 1,275 chironomids taken from the seven Cyanamid Canada stations, the great majority were pollution tolerant taxa. The low biotic diversity and the presence of considerable numbers of pollution tolerant benthic macroinvertebrates in combination with the chemical evidence of pollutants in the sediments near many of these Cyanamid discharge sites were reasons for classifying these sites as 'impaired' as defined by the International Joint Commission.

Physical environment of the Gulf relevant to marine pollution: An overview

The most important physical aspects of the Gulf with respect to effects of marine pollution are its semi-enclosed, shallow nature and its arid setting. The Gulf is principally a sedimentary basin whose substrate is mainly biogenic, with outcrops of older limestone, and with a few actively growing reefs. It is relatively shallow, so that almost all parts of it lie within the photic zone. Its enclosed nature means that it has a low rate of water exchange (up to 5 years), and large parts of it experience extremes of salinity and temperature which have considerable effect on the marine communities. Pelagic productivity is typical for waters of this latitude, though the high productivity values commonly attributed to the Gulf refer to benthic components rather than to the main water mass. It suffered complete drying out in the late Pleistocene, so that its present relatively low biotic diversity is perhaps due as much to its relatively short existence in Recent time as much as to the extremes of environmental conditions which it experiences.

Seasonal dynamics and productivity of Tanytarsus barbitarsis Freeman (Diptera: Chironomidae) in the benthos of a shallow, saline lake

The chironomid Tanytarsus barbitarsis is the only abundant benthic species in Lake Werowrap, western Victoria, a small, shallow, highly alkaline lake in which high, fluctuating salinities (c. 36-56 g/l) impose an extremely low biotic diversity. Between successive Octobers in 1969 and 1970, the chironomids passed through about seven generations, attaining numerical densities in excess of 140,000/m². Seasonal fluctuations in density were attributed to emergence, available food, and predation by a dytiscid, Necterosoma penicillatum, occurring in high densities around the rocky marginal areas of the lake. Estimated annual net production, exclusive of mortality and first and second instar biomass, amounted to about 320 kcal/m²/yr. This is perhaps the highest estimate recorded for an inland aquatic macrobenthos community; it is especially remarkable in that evidence from salinity tolerance experiments suggests that the lake is not an optimal environment for the species.

INFLUENCE OF ZINC ON PERIPHYTIC COMMUNITIES

The glass‐slide technique was used in a 14‐week study to show the effects of 4 concentrations of zinc on periphytic communities in 4 outdoor canals supplied with running pond water containing its natural biota. No species was found that could be considered an indicator of zinc. The effect of adding 1 mg/liter or more of zinc was to reduce the number of dominant species. A geometric regression of the average number of dominant algal species was found beginning with the control, with no added zinc, and proceeding from that to the largest concentration of zinc. A relatively large concentration of zinc resulted in comparatively low biotic diversity. Fungi and slime‐forming bacteria produced a large standing crop in the largest zinc concentration, apparently by digesting the killed incoming phytoplankters that were used as their food.