The mechanical effects of water flow on fish eggs and larvae

The impact of mechanical stresses upon ichthyoplankton entrained in power plant cooling systems has long been considered negligible. Arguments and evidence exist, however, to show that such a supposition is not universally true, especially in nuclear power plants. The mechanisms of mechanical damage can be detailed in terms of pressure change, acceleration, and shear stress with in the fluid flow field. Laboratory efforts to quantify the effects of mechanical stress have been very sparse. A well-planned bioassay is urgently needed. (PDF has 11 pages.

Modeling the Chesapeake Bay and Tributaries: a synopsis

The last decade has seen the development and application of a spectrum of physical and numerical hydrographic models of the Chesapeake Bay and its tributaries. The success of the James River Hydraulic Model has initiated the construction of an estuarine hydraulic model of the entire Chesapeake System. Numerical analogues for hydrographic behavior and contaminant dispersion in one-, two-, and three dimensional model estuaries exist for various regions of the Bay. From an engineering viewpoint, one dimensional models are sufficiently advanced to be routinely employed in aiding management decisions. Bay investigators are playing leading roles in the development of two- and three-dimensional models of estuarine flows

Some effects of tropical storm Agnes on water quality in the Patuxent River estuary

A post Agnes study emphasizing environmental factors...weekly sampling at eight stations from 28 June to August 30, 1972. Spatial and temporal changes in the distribution of many factors, e.g., salinity, dissolved oxygen (DO), seston, particulate carbon and nitrogen, inorganic and organic fractions of dissolved nitrogen and phosphorus, and chlorophyll a were studied and compared to earlier extensive records. Patterns shown by the present data were compared especially with a local heavy storm that occurred in the Patuxent drainage basin during July 1963. Some interesting correlations were observed in the data. (PDF has 39 pages.

Some effects of Hurricane Agnes on water quality in the Patuxent River Estuary

A post-Agnes study that emphasized environmental factors was carried out on the Patuxent River estuary with weekly sampling at eight stations from 28 June t o 30 August 1972. Spatial and temporal changes in the distribution of many factors , e.g., salinity , dissolved oxygen, seston, particulate carbon and nitrogen, inorganic and organic fractions of dissolved nitrogen and phosphorus, and chlorophyll a were studied and compared t o extensive earlier records. Patterns shown by the present data were compared especially with a local heavy storm that occurred in the Patuxent drainage basin during July 1969. Estimates were made of the amounts of material contributed via upland drainage. A first approximation indicated that 14.8 x l0 (3) metric tons of seston were contributed t o the head of the estuary between 21 and 24 June. (PDF contains 46 pages

Toward canonical trophic aggregations

The attractiveness of the trophic concept is that it was the first attempt at a holistic perspective on an ecosystem which met with any degree of success. Just as temperature, pressure, and volume allow one to characterize the incomprehensible multitude of particulate motions in a simple gas, the hope is that a small set of figures, such as trophic storages or trophic efficiencies, permit one to compare two ecosystems with overwhelmingly disparate complexities. Thus, if it were possible to demonstrate that an arbitrary network of ecosystem flows could be reduced to a trophic configuration, the aggregation process thus defined would become a key component of the evolving discipline of "macroscopic ecology" (see also Odum 1977 and Ulanowicz 1979)

Segmentation of Chesapeake Bay: a representative exercise

The goal of the CRC/RANN Waste Water Program is to provide the tools to management agencies which will enable them to make sound quantitative decisions on the siting of future sewage outfalls and the upgrading or elimination of existing sewage treatment plants. Obviously, the available funds do not permit extensive field studies at every possible outfall site. Therefore, some system is needed which will allow data to be transferred from one area to other areas within the Bay which have similar characteristics. A system of segmentation ., as suggested by Dr. D. W. Pritchard, was chosen by the Scientific Management Advisory Committee as the appropriate vehicle to achieve this transferability of the data. The following sections describe the philosophy for segmentation., the criteria to be used and two examples of the segmentation process using the Patuxent and Elizabeth River Estuaries as models

Modeling Environmental Stress

The word stress when applied to ecosystems is ambiguous. Stress may be low-level, with accompanying near-linear strain, or it may be of finite magnitude, with nonlinear response and possible disintegration of the system. Since there are practically no widely accepted definitions of ecosystem strain, classification of models of stressed systems is tenuous. Despite appearances, most ecosystem models seem to fall into the low-level linear response category. Although they sometimes simulate systems behavior well, they do not provide necessary and sufficient information about sudden structural changes nor structure after transition. Dynamic models of finiteamplitude response to stress are rare because of analytical difficulties. Some idea as to future transition states can be obtained by regarding the behavior of unperturbed functions under limiting strain conditions. Preliminary work shows that, since community variables do respond in a coherent manner to stress, macroscopic analyses of stressed ecosystems offer possible alternatives to compartmental models

Eutrophication in the Chesapeake Bay

The most critical long-term threat to the continued health of the Chesapeake Bay is the addition of excess nutrients to the estuarine waters. Other problems, such as Kepone and the disappearance of aquatic vegetation (which is possibly linked with nutrient loading), may steal our attention for short periods,but these difficulties will, hopefully, recede in due time. The projected growth of population in the near environs of the Bay, however, indicates that,as a problem, eutrophication will probably continue well into the next centur

Effects of shear on eggs and larvae of striped bass, morone saxatilis, and white perch, M. americana

Shear stress, generated by water movement, can kill fish eggs and larvae by causing rotation or deformation. Through the use of an experimental apparatus, a series of shear (as dynes/cm2)-mortality equations for fixed time exposures were generated for striped bass and white perch eggs and larvae. Exposure of striped bass eggs to a shear level of 350 dynes/cm2 kills 36% of the eggs in 1 min; 69% in 2 min, and 88% in 4 min; exposure of larvae to 350 dynes/cm2 kills 9.3% in 1 min, 30.0% in 2 min, and 68.1% in 4 min. A shear level of 350 dynes/cm2 kills 38% of the white perch eggs in 1 min, 41% in 2 min, 89% in 5 min, 96% in 10 min, and 98% in 20 min. A shear level of 350 dynes/cm2 applied to white perch larvae destroys 38% of the larvae in 1 min, 52% in 2 min, and 75% in 4 min. Results are experimentally used in conjunction with the determination of shear levels in the Chesapeake and Delaware Canal and ship movement for the estimation of fish egg and larval mortalities in the field

A Synoptic View of a Coastal Plain Estuary.

During October, 1972 the Patuxent River Estuary was monitored intensively and synoptically over two tidal cycles to determine the spatial and temporal patterns of various hydrodynamic, chemical and biological features. Forty-one depths at eleven stations along nine transects were sampled simultaneously at hourly intervals for salinity, temperature, dissolved oxygen, chlorohyll a, particulate nitrogen, nitrate, nitrite, total kjeldahl nitrogen, ammonia, particulate carbohydrate, dissolved organic carbon, total hydrolizable phosphorous, dissolved inorganic phosphorous, suspended sediment, particle size distribution, and zooplankton. Tidal velocity was continuously monitored at each depth by recording current meters. Riverine input and meteorological conditions were relatively stable for two weeks preceeding the deployment. This communication describes the calculation of the intrinsic rates of change of the observed variables from their measured distributions in the Estuary. The steady-state, one-dimensional equation of species continuity is employed to separate the advection and tidal dispersion of a hydrodynamically passive substance frbm its intrinsic rate of change at point. A new spatial transform is introduced for the purpose of interpolation and extrapolation of data.The intrinsic rate of change profiles reveal a region of heavy bloom activity in the upper estuary and a secondary bloom near the point in the River that most of the suspended material settles out. The changes in ammonia and nitrates are highly correlated to the productivity patterns. Phosphorous rates are less closely correlated to productivity. The perturbations that the Chalk Point steam electric power plant have on the heat and oxygen balances are easily discernible