Johannes Rick

The Impacts of Pulsed Reintroduction of River Water on a Mississippi Delta Coastal Basin

Abstract During the twentieth century about 25% of the wetlands of the Mississippi delta was lost, partially a result of isolation of the river from the delta. River diversions are being implemented to reintroduce river water to the delta plain. We synthesize here the results of extensive studies on a river diversion at Caernarvon, Louisiana, one of the largest diversions in the delta.

Nutrient-phytoplankton-zooplankton models with a toxin

Models of nutrient-plankton interaction with a toxic substance that inhibits either the growth rate of phytoplankton, zooplankton or both trophic levels are proposed and studied. For simplicity, it is assumed that both nutrient and the toxin have the same constant input and washout rate as the chemostat system. The effects of the toxin upon the existence, magnitude, and stability of the steady states are examined. Numerical simulations demonstrate that the system can have multiple attractors when the phytoplanktons nutrient uptake rate is inhibited by the toxin.

Occurrence of a Cylindrospermopsis Bloom in Louisiana

ABSTRACT Cylindrospermopsis raciborskii occurs predominantly in tropical to subtropical freshwaters but appears to be spreading to temperate regions. After the hurricanes of 2005, a bloom of this organism took place in Lake Dauterive and Lake Fausse Pointe in Louisiana. The cyanobacterium dominated the phytoplankton community for three months. Of the three known morphotypes (straight, coiled and spiral) only coiled and spiral were found. In June 2006, 60% of the organisms were of the spiral morphotype but the relative abundance of this morphotype decreased dramatically within the month of June. However, the average density for both morphotypes remained the same until September. Densities (up to 160,000 cells/mL) significantly exceeded the threshold for toxicity. Because the sampled region offers optimal light and nutrient conditions, it is likely that C. raciborskii has been established in this region and future blooms can be expected. Therefore, a monitoring program should be implemented.

Aquatische Ökosysteme: Nordsee, Wattenmeer, Elbeästuar und Ostsee

Langzeitbeobachtungen von aquatischen Okosystemen zeigen nicht nur eine hohe Variabilitat, sondern auch graduelle Anderungen und sog. Regimeshifts: sprunghafte Anderungen im Funktionieren des gesamten Okosystems. Sowohl die naturliche Variabilitat hydrodynamischer und atmospharischer Prozesse auf verschiedenen Zeitskalen als auch menschliche Einflussnahmen wie beispielsweise CO2-Ausstos, Fischerei, Deichbau, Vertiefungen oder Eutrophierung tragen zu dieser komplexen okologischen Dynamik bei (z. B. Emeis et al. 2015).

Long-term physical an hydrochemical measurements at Sylt Roads LTER (1973-2013), Wadden Sea, North Sea, links to data sets.

The SYLT ROADS LTER pelagic time series covers physical and hydrochemical parameters in the Sylt-ROmO Bight, Wadden Sea, North Sea. Since its inception in 1973 Sea Surface Temperature (SST), Salinity, Ammonia, Nitrite, Nitrate, Soluble Reactive Phosphorus (SRP) and Silicate were measured on a biweekly basis. The other parameters were introduced later (pH - since 1979, dissolved organic nitrogen (DON) - since 1996, dissolved organic phosphorus (DOP) - since 2001, chlorophyll a - since 1979, suspended particulate matter (SPM) - since 1975) and in case of dissolved oxygen were discontinued (1979-1983). During the years 1977, 1978 and 1983 no sampling took place. Since the start of continuous sampling in 1984 the sea surface temperature in the bight has risen by 1.16 oC, with the highest increases during the fall months while the pH decreased by 0.248 units. Summer and fall salinities are generally significantly elevated compared to spring and winter conditions. Dissolved nutrients as ammonia, nitrite, nitrate and reactive phosphorus (SRP) showed periods of elevated eutrophication (1973 - 1998) while silicate displayed a different development with significantly elevated levels of the winter data since 1999. Interestingly phytoplankton sum parameters did not mirror these huge nutrient changes, as a seasonal comparison of the two eutrophication conditions showed no significant differences with regard to chlorophyll, which is ultimately triggered by an important change in nutrient limitation during the time series: Till 1988 the phytoplankton was primarily limited by silicate, while since 1999 SRP limitation became increasingly important.

Semi-quantitive microplankton analysis (Sylt Roads Time Series) in the Wadden Sea off List, Sylt, North Sea in 1987

See data in other version: 1987 - https://doi.pangaea.de/10.1594/PANGAEA.861296 / 1988 - https://doi.pangaea.de/10.1594/PANGAEA.861297 / 1989 - https://doi.pangaea.de/10.1594/PANGAEA.861298 / 1990 - https://doi.pangaea.de/10.1594/PANGAEA.861299 / 1991 - https://doi.pangaea.de/10.1594/PANGAEA.861300 / 1992 - https://doi.pangaea.de/10.1594/PANGAEA.861301 / 1993 - https://doi.pangaea.de/10.1594/PANGAEA.861302 / 1994 - https://doi.pangaea.de/10.1594/PANGAEA.861303 / 1995 - https://doi.pangaea.de/10.1594/PANGAEA.861304 / 1996 - https://doi.pangaea.de/10.1594/PANGAEA.861305 / 1997 - https://doi.pangaea.de/10.1594/PANGAEA.861306 / 1998 - https://doi.pangaea.de/10.1594/PANGAEA.861307 / 1999 - https://doi.pangaea.de/10.1594/PANGAEA.861308 / 2000 - https://doi.pangaea.de/10.1594/PANGAEA.861309 / 2001 - https://doi.pangaea.de/10.1594/PANGAEA.861310

Semi-quantitive microplankton analysis (Sylt Roads Time Series) in the Wadden Sea off List, Sylt, North Sea in 2002

See data in other version: 2002 - https://doi.pangaea.de/10.1594/PANGAEA.860409 / 2003 - https://doi.pangaea.de/10.1594/PANGAEA.860410 / 2004 - https://doi.pangaea.de/10.1594/PANGAEA.860411 / 2005 - https://doi.pangaea.de/10.1594/PANGAEA.860412 / 2006 - https://doi.pangaea.de/10.1594/PANGAEA.860413 / 2007 - https://doi.pangaea.de/10.1594/PANGAEA.860414 / 2008 - https://doi.pangaea.de/10.1594/PANGAEA.860415 / 2009 - https://doi.pangaea.de/10.1594/PANGAEA.860416 / 2010 - https://doi.pangaea.de/10.1594/PANGAEA.860417 / 2011 - https://doi.pangaea.de/10.1594/PANGAEA.860418 / 2012 - https://doi.pangaea.de/10.1594/PANGAEA.860419 / 2013 - https://doi.pangaea.de/10.1594/PANGAEA.860420

Plankton-toxin interaction with a variable input nutrient.

A simple model of phytoplankton–zooplankton interaction with a periodic input nutrient is presented. The model is then used to study a nutrient–plankton interaction with a toxic substance that inhibits the growth rate of plankton populations. The effects of the toxin upon the existence, magnitude, and stability of the periodic solutions are discussed. Numerical simulations are also provided to illustrate analytical results and to compare more complicated dynamical behaviour.