Delaware Estuary Cruise Database

Explanation of Delaware Estuary Cruise Database
from the Laboratory of Jonathan H. Sharp

This is intended as a brief description of the data in the Excel database. It does not include details of methods and statistics about them. Data are given for cruise sampling from 1978 through 2003. A list of the research cruises with dates, stations samped, and extra sampling is given in the table (click here). Most parameters are listed in molar units so that 1 µM of an element is equal to 1 µg atomic weight units per L of water (1 µ-at/L); multiplying µM by the atomic weight will give µg/L. Separation between particulate and dissolved matter was originally performed with Whatman GF/C filters, currently GF/F filters are used – with the exception of iron, none of the parameters measured in the estuarine environment are affected by this change in filter size. The data columns in order are:

Record ID - Sequential from 9,219 to 11,283.
Cruise Name – Name and number of individual sampling cruise.
Station - Designation of sampling station.
Depth of Sample – Nominal depth of sample. Most samples are from the surface (center of 10 L Niskin water bottle is usually 0.5 to 1.5 m below water line, depths are listed to nearest meter).
Date – date that station's sample(s) was collected.
JD - Julian Day - day of the year.
Time – Local time of collection (trip time for last surface sample bottle, also time for latitude and longitude recording).
Lat, Long = Latitude and longitude – in degrees with decimal degrees. Locations initially determined from Loran fixes, later ones from satellite navigation, and most recent ones by GPS. Approximated distances used on occasion of poor fix – see list at end of this writeup.
Distance – Distance from mouth of Delaware Bay along estuarine axis in km – equivalent to DRBC River Mile as km.
Temperature (ºC) is from CTD system (since mid-1980s); older ones from reversing thermometers on Niskin bottles.
Salinity – Originally listed as parts per thousand, currently this is a dimensionless parameter on the Practical Salinity Scale (psu). Measured by laboratory salinometer until 1990s; since then from CTD system. Salinity measurement prior to the Scenic cruises relied on an algorithm for converting from conductivity ratio with a remainder, giving negative salinity at very low ionic concentration. On those prior cruises, salinity data are removed for any values less than 0.05. After 1985, algorithms with no remainder were used for conversion of both conductivity ratio (laboratory salinometer) and direct conductivity measurements (CTD system).
DO = Dissolved oxygen (as µg-at O/L – 2 µgat O = 1 µM O₂).
O-Sat = Percent saturation of measured DO based on equilibration at ambient temperature and salinity of sample when collected.
DIC = total dissolved inorganic carbon (also referred to as TCO₂ or ΣCO₂) in µM C. DIC concentration was estimated from pH and alkalinity for earliest cruises and then by direct measurement with acid sparging and infrared analysis of CO₂(1986 - present).
NO₂ = nitrite nitrogen – colorimetric method (µM N).
NO₃ = nitrate nitrogen – colorimetric method (µM N).
NH₄ = ammonium nitrogen – colorimetric method (µM N).
PO₄ = phosphate - also called soluble reactive phosphorus – colorimetric method (µM P).
Si = silicate – colorimetric method (µM Si).
DOC = dissolved organic carbon - (total organic carbon of filtered sample) (µMC).
Cl = chloride concentration – measured by argenometric titration, as µM Cl.
Ca = calcium concentration – measured by EDTA titration, as µM Ca.
pH = pH measured immediately upon collection in sample free of air space.
Akal = total alkalinity – measured by titration, as µ equivalents/L.
Fe = dissolved iron – measured by colorimetric method, as µM Fe.
Seston = total suspended sediments (gravimetric measure on 1 µm pore size Nuclepore filter), as mg/L net weight.
PC = particulate carbon - (measured by high temperature combustion and micro-Pregl/micro-Dumas conversion with final measure as CO₂, initially by gas chromatography, currently by mass spectrometery), as µM C.
PN = particulate nitrogen - (measured simultaneously with the PC as N₂ after conversion), as µM N.
Light = light attenuation calculated from – ln of total visible light energy versus depth. Measured with PAR quantum meter. Listed as reciprocal of depth.
Secchi depth = disappearance depth of Secchi meter disc with manual lowering.
Chlor a = chlorophyll a concentration of filtered sample extracted in 90% acetone and measured by filter flourometer, in µg chlorophyll/L.
APROD = areal production in mmoles C/m²/d.
VPROD = maximum volumetric production in µmoles C/L/d.
P/B = production (VPROD converted to µg C/L/d) divided by µg Chlor/L.

Primary production was measured by isotopic tagging (with NaH¹⁴CO₃) a series of water samples that were incubated with simulated in-situ conditions on the deck of the ship in an incubator table with ambient water temperature and light fields of ambient light with attenuation in six steps from full intensity to 3% of full intensity. Incubations were for 24 hours. The six light levels were simulated and production was integrated over depth by matching light levels to depth in the water column using the light attenuation measured with a quantum meter. The individual light bottle that displayed the maximum primary production, usually that with 100% or 60% full illumination was designated the maximum volumetric production – on very bright days, the phytoplankton occasionally become acclimated to slightly lower light levels and show inhibition at full light intensity.

Stations where there were difficulties with exact location and for which latitude and longitude were estimated are:

Scenic 2 – Station 7
Scenic 10 – Station 12
Scenic 13 – Stations 5, 6, and 7
Scenic 23 – Station 9
Colloid 8 – All Stations
Colloid 10 – All Stations

To enter database click here. (Database is in Microsoft Excel)

Updated: June 5, 2006