Effects of coastal eutrophication on the spawning grounds of the Baltic herring in the SW Archipelago of Finland

In the last 14 years, trapnet catches of the Baltic herring (Clupea harengus membras L.) have decreased drastically in the inner zones of the bays studied, but increased in the outer zones in the sea area of Turku, SW Finland. We deduce that the reasons for the decrease of catches have been eutrophication and sedimentation of the bays. The spawning grounds of the Baltic herring were studied by SCUBA-diving in the sea area of Turku in 1981-86. We studied 134 locations but found eggs in only 20 locations. Herring did not lay eggs on all suitable grounds, but regularly and intensively used some few locations from year to year. The most important spawning grounds were situated in the outer zones of the bays. We found eggs at 0-8 meters depth. In the inner parts of the bays, we did not find eggs with the exception of one shore, which is kept free of sediments by water currents. The spawning grounds comprised mainly sand and gravel. Most of them were covered by vegetation. Eggs were attached to Cladophora glomerata, Potamogeton perfoliatus, and red algae Furcellaria Jumbricalis and Phyllophora truncata. In the innermost zones of the bays the original littoral hard bottoms have changed to soft, muddy bottoms and consequently no eggs could be found there

The virtual AirDyn: a simulation technique for evaluating the aerodynamic impact of ship superstructures on helicopter operations

This paper describes a simulation technique that has been developed to quantify the unsteady forces and moments that are imposed onto a maritime helicopter by a ship's airwake during a deck landing. An unsteady CFD-generated airwake, created using a CAD model of the ship, is integrated with a flight dynamics model of a helicopter. By holding the helicopter at a fixed position in the airwake it is possible to quantify the unsteady forces and moments imposed on the aircraft. The technique is therefore a software-based airwake dynamometer, and has been called the virtual AirDyn. As well as determining the mean loads, from consideration of the unsteady loads in the closed-loop pilot response frequency range of 02-2Hz it is also possible to quantify the magnitude of the unsteady disturbance in each axis. The loads are also indicators of the control activity the pilot would have to exert to maintain aircraft position and attitude. By placing the virtual AirDyn at different positions around the landing deck in different wind conditions, it is able to quantify the effect of the airwake on the mean and unsteady loads. The quantified loads can be explained by examining the CFD-generated flow field, and the geometric features on the ship's superstructure that gave rise to them can be identified. The virtual AirDyn is therefore a tool that can be used to evaluate and inform ship design for maritime helicopter operations

UNPRECEDENTED BLOOM OF TOXIN-PRODUCING CYANOBACTERIA IN THE SOUTHERN BAY-DELTA ESTUARY HAS NEGATIVE IMPACT ON THE AQUATIC FOOD-WEB

California’s Sacramento-San Joaquin Delta is an expansive fresh-water tidal estuary that is part of the San Francisco Estuary, the largest estuary on the US Pacific coast. Recently, there has been a collapse in the pelagic fish community in the San Francisco Estuary, known as the pelagic organism decline (POD). Blooms of the cyanobacteria Microcystis, which often produce the cyanotoxin microcystin, were first documented in the Sacramento-San Joaquin Delta in 1999. Cyanotoxins have been suspected as one contributing factor to POD. It has been proposed that microcystin could be contributing to POD directly though poisoning of fish or indirectly by affecting zooplankton and other food sources. Copepods, especially E. affinis and P. forbesi are important food sources for larval POD species. Delta and longfin smelt, threatened species, feed on rotifers and other small organisms the first weeks after hatching

UNPRECEDENTED BLOOM OF TOXIN-PRODUCING CYANOBACTERIA IN THE SOUTHERN BAY-DELTA ESTUARY HAS NEGATIVE IMPACT ON THE AQUATIC FOOD-WEB

California’s Sacramento-San Joaquin Delta is an expansive fresh-water tidal estuary that is part of the San Francisco Estuary, the largest estuary on the US Pacific coast. Recently, there has been a collapse in the pelagic fish community in the San Francisco Estuary, known as the pelagic organism decline (POD). Blooms of the cyanobacteria Microcystis, which often produce the cyanotoxin microcystin, were first documented in the Sacramento-San Joaquin Delta in 1999. Cyanotoxins have been suspected as one contributing factor to POD. It has been proposed that microcystin could be contributing to POD directly though poisoning of fish or indirectly by affecting zooplankton and other food sources. Copepods, especially E. affinis and P. forbesi are important food sources for larval POD species. Delta and longfin smelt, threatened species, feed on rotifers and other small organisms the first weeks after hatching