Long-term Changes In Distribution Research Articles

Hydrometeorological conditions drive long-term changes in the spatial distribution of Potamogeton crispus in a subtropical lake.

Globally, anthropogenic disturbance and climate change caused a rapid decline of submerged macrophytes in lake ecosystems. Potamogeton crispus (P. crispus), a species that germinates in winter, explosively expanded throughout many Chinese lakes, yet the underlying mechanism remained unclear. Here, this study examined the long-term changes in the distribution patterns of P. crispus in Lake Gaoyou by combining remote sensing images and hydrometeorological data from 1984 to 2022 and water quality data from 2009 to 2022. It aims to unravel the relationships between the distribution patterns of P. crispus and hydrometeorological and water quality factors. The results showed that the area of P. crispus in Lake Gaoyou showed a slight increase from 1984 to 2009, a marked increase from 2010 to 2019, followed by a decline after 2020. Spatially, P. crispus was primarily distributed in the western and northern parts of Lake Gaoyou, with less distribution in the central and southeastern parts of the lake. Wind speed (WS), temperature (Temp), water level (WL), ammonia nitrogen (NH3-N), and Secchi depth (SD) were identified as the key factors regulating the variation in the P. crispus area in Lake Gaoyou. We found that the P. crispus area showed an increasing trend with increasing Temp, WL, and SD and decreasing WS and NH3-N. The influence of environmental factors on the area of P. crispus in Lake Gaoyou varied among seasons. The results indicated that hydrometeorology (WS, Temp, and WL) may override water quality (NH3-N and SD) in driving the succession of P. crispus distribution. The findings of this study offer valuable insights into the recent widespread expansion of P. crispus in shallow lakes across Eastern China.

大都市におけるモンシロチョウとスジグロシロチョウの分布の変遷 : I.東京都の場合

大都市におけるモンシロチョウとスジグロシロチョウの分布の変遷 : I.東京都の場合

Long-term changes in distribution and abundance of submerged aquatic vegetation and dreissenid mussels in Long Point Bay, Lake Erie

Abstract Submerged aquatic vegetation (SAV) in Inner Long Point Bay (LPB), Lake Erie provides food and habitat for a diversity of fish and wildlife. The abundance and community structure of SAV often are used as bioindicators of ecosystem health. Colonization and increases in abundance of zebra mussels ( Dreissena polymorpha ) at LPB in the early 1990s increased water clarity which changed the SAV community. We used data from studies in 1976, 1991, and 1992 and sampled LPB in 2009 to quantify changes in abundance and occurrence of SAV, determine densities of zebra mussels, and model influences of year, water depth and substrate type on the probability of detection of SAV. We detected 96% decrease in mean (± SE) mussels/m 2 between 1992 (457 ± 86) and 2009 (19 ± 2). With the exception of slender pondweed ( Potamogeton pusillus ), the five most abundant SAV species in 1992 had decreased by 2009. Water depth and substrate type influenced probability of detection of all SAV species, excluding Najas spp. , suggesting that changes in Lake Erie water levels and sediment loading may influence future SAV communities. Decreased abundance of filter feeding mussels is consistent with increased eutrophication and changes in SAV in LPB. Carrying capacity of LPB for waterfowl and other fish and wildlife that use and eat SAV and mussels increased during the mid-1990s, but has since decreased.

Long-Term Changes in Distribution and Frequency of Aquatic Vascular Plants and Charophytes in an Estuary in the Baltic Sea

The long-term impact of natural and human-induced large-scale changes on aquatic phanerogams and charophytes has remained mostly unstudied in the Baltic Sea, largely because of a lack of historical data. A vegetation data set based on transects in an estuary in the western part of the Gulf of Finland studied in the 1930s–1940s, however, exists. We re-surveyed 91 of these transects in 2005 and 2007. The historical data set included 60 species and the contemporary 52 species. The species were classified into increasing, decreasing or unchanged according to the change in their occurrence frequencies. A significant frequency change was found for 31 of the 50 (62%) species which were present in both surveys. The proportion of species/growth forms with high-nitrogen and low-light preferences increased, whereas that of species/growth forms preferring oligotrophic conditions and species of shallow waters decreased. In the area, the species expanded their distribution ranges mainly towards the open sea. Eutrophication, reduced grazing pressure and shore overgrowth by Phragmites australis are suggested as the main reasons for the observed changes. In addition, increased boating and shore-construction activities contributed to the long-term floristic changes.

Factors associated with long-term changes in distribution of black-tailed prairie dogs in northwestern Mexico

The area occupied by colonies of the black-tailed prairie dog (Cynomys ludovicianus; BTPD henceforth) in northwestern Mexico was dramatically reduced between 1988 and 2005. We conducted a quantitative assessment of the distributional changes of these BTPD colonies during the periods 1988–2000 and 2000–2005 focusing on the potential roles of plant biomass, landscape configuration, habitat loss, and habitat suitability. We used remote sensing and GIS tools to characterize habitat and landscape conditions at areas of extinction and persistence at the beginning of each period. Based on this information, we contrasted areas of extinction and persistence within single BTPD colonies, and used logistic regression to model extinction of entire colonies. The greatest levels of reduction, fragmentation and extinction of colonies occurred between 1988 and 2000. The trend of reduction continued between 2000 and 2005 because the largest colony became smaller and fragmented, driving the area down, however, the rest of the towns showed a marginal increase. During the first period, extinction of entire colonies was higher in smaller colonies occupying low-biomass areas. Both extinction models and raw data indicate that colony area lost to agriculture and urbanization was relatively low for both periods. Because the period exhibiting the highest colony area loss coincided with a severe period of drought (1994–1995), we hypothesized that an unusually high food shortage could be the driving force behind this generalized reduction in colonies. Our results suggest that BTPD populations are sensitive to size and isolation effects mainly in the context of severe drought. Because changes in precipitation have profound impacts on plant productivity and composition in arid ecosystems, BTPD populations at the southernmost edge of their geographic range are especially vulnerable to drought and desertification processes, and therefore to climate disruption.

Long-term changes in distribution and demographic composition of thornback ray,Raja clavata, in the northern and central Adriatic Sea

Population structure and distribution of the thornback ray, Raja clavata, L. 1758, in the northern and central Adriatic Sea were described based on data from bottom trawl surveys conducted in the area between 1996 and 2006 within the scope of the ‘MEDITS’ project. R. clavata was caught at depths between 23 and 270 m; highest abundance and density indices were recorded at a depth stratum 50–100 m. The sex ratio was close to 1 : 1. Length at first sexual maturity for both sexes was calculated. Length–weight relationships were obtained for males, females and the whole sample. Calculated parameters of the length–weight ratio showed a positive allometry for both sexes. The recent state of the population was compared with data from the 1948–49 ‘Hvar’ expedition. The comparison revealed that significant changes have occurred in distribution and abundance of R. clavata in the Adriatic Sea since the time of the ‘Hvar’ expedition. During the 1948–49 ‘Hvar’ expedition R. clavata was distributed throughout the entire continental shelf; during the 1996–2006 MEDITS expedition the species was found only in restricted areas and with much lower abundances. Significant changes also occurred in the demographic composition of the population. All described changes indicate an over-fishing of the thornback ray in the Adriatic Sea, a result of the high fishing intensity to which the species has been exposed for the past 60 years.

Temporal and spatial distribution of chironomid larvae and oligochaetes in two Dutch storage reservoirs

Long-term changes in distribution and taxonomic composition of chironomid larvae and oligochaetes in two water storage reservoirs in The Netherlands were studied. A succession among the chironomid species was observed. In the last 10–15 years chironomid densities varied. Compared with other lakes chironomid densities were high. Densities of chironomids were higher in the littoral zone than in the profundal zone. The opposite was found for oligochaetes. Densities and composition of the chironomid fauna in the two reservoirs were similar.Procladius, Tanytarsus andHarnischia dominated at all depths. However, pupal exuviae samples showed some differences in chironomid taxonomic composition between the two reservoirs. Orthocladiinae, rarely found in bottom samples, abounded in pupal exuviae samples.

Distribution of physical properties below the level of seasonal influence in the eastern North Pacific Ocean

North-south temperature, salinity, and oxygen sections for the eastern North Pacific Ocean were constructed from data obtained during the 1957 and 1958 cruises of the M.V. Brown Bear and have been compared with data obtained 29 years earlier by the Carnegie. Long-term changes in distribution of these properties have been investigated by using all the pertinent data available for the years between the Carnegie and Brown Bear expeditions. No significant trends appear in the subarctic water; however, there is a possibility of a shifting of the transition zone between the subarctic and equatorial waters.