Movement and Quality of Long Island Sound Waters

Home , Hell Gate, Long Island Sound

MARINE MOVEMENT SCIENCES ... RESEARCH AND CENTER QUALITY OF LONG STATE ISLAND UNIVERSITY OF SOUND NEW YORK WATERS, 1971

TECHNICAL BY REPORT C. D. HARDY SERIES :# 17

PREPARED WITH SUPPORT FROM THE NASSAU-SUFFOLK REGIONAL PLANNING BOARD

'"- - I Technical Report No. 17

MOVEMENT AND QUALITY OF LONG ISLAND SOUND WATERS, 1971

C. D. Hardy

November 1972

Prepared with support from the Nassau-Suffolk Regional Planning Board

Marine Sciences Research Center State University of New York Stony Brook, New York 11790 ABSTRACT

The hydrographic features of lower New York Bay, upper New York Bay, the East River, Long Island Sound, and Block Island Sound are described.

Winter-formed bottom water exhibits a seasonal lag in warming in the Central Basin of Long Island Sound. The persistence into summer of this colder and denser bottom layer indicates limited mixing.

The stagnation of this bottom water is promoted by the seasonal formation of a weak to moderate thermocline and the inhibition of exchange with Block Island Sound water by the presence of a submarine ridge.

A heavy biological oxygen demand is imposed upon the bottom water by the introduction of oxidizable organic matter from the New York metropolitan area.

The depletion of dissolved oxygen is correlated on an annual basis in accord with the frequency and strength of winds. In summer, prolonged periods of calm intensify the vertical stratification, causing seriously lowered dissolved oxyge n concentrations in the bottom layer.

Maximum concentrations of nutrients (ammonia, ure a, orthophosphate) for the region were found in the upper East River, r e flecting the fact that 43 percent of the sewage from the New York City municipal system discharges into the upper East River. Urea concentrations in the East River we re higher than previously reported. The presence of urea at these concentrations reflects the untreate d quality of sewage entering this water body.

A two-layered transport system is proposed by which the n e t transport of East River water into Long Island Sound may be explained. This estuarine circulation provides a mechanism by which East River pollutants e nter Long Island Sound. CONTENTS Page INTRODUCTION . . . 8

ACKNOWLEDGEMENTS . 8

SAMPLING AND ANALYTICAL TECHNIQUES . 8

WATER TEMPERATURE 9

SALINITY AND DENSITY . 16

DISSOLVED OXYGEN 24

REACTIVE PHOSPHATE . . 28

AMMONIA 28

UREA 33

CHLOROPHYLL 33

TURBIDITY 41

WATER MASS TYPES . 41

MATTITUCK SILL 43

WIND 53

CIRCULATION 57

REFERENCES 63

APPENDIX - Formulas for Metric - English 65 Conversion LIST OF ILLUSTRATIONS

Figure Page 1 Geographic Features of Long Island Sound 1

2 Geographic Features of New York Harbor and East River 2

3 Station Locations of Cruise 7101 3 4 Station Locations of Cruise 7101, New York Harbor 4 and East River

5 Station Locations of Cruise 710701 5

6 Station Locations of Cruise 7102 6

7 Station Locations of Cruise 7102, New York Harbor 7 and East River

8 Surface Temperature, Cruise 7101 10

9 Temperature Profile, Cruise 7101 11

10 Wind Data at Execution Rock, N.Y. 13

11 Surface Temperature, Cruise 7102 14

12 Temperature Profile, Cruise 7102 15

13 Surface Salinity, Cruise 7101 17

14 Salinity Profile, Cruise 7101 18

15 Temperature and Salinity Profiles, East River, 19 Cruise 7101

16 Density Profile, Cruise 7101 20

17 Surface Salinity, Cruise 7102 21

18 Salinity Profile , Cruise 7102 22

19 Density Profile, Cruise 7102 23

20 Surface Dissolved Oxygen, Cruise 7101 25

21 Surface Dissolved Oxygen Profile, Cruise 7102 26

22 Dissolved Oxygen Profile, Cruise 7102 27

23 Reactive Phosphate, Cruise 7101 29

24 Reactive Phosphate, Cruise 7102 30

25 Ammonia, Cruise 7101 31

26 Ammonia, Cruise 7102 32

27 Urea, Cruise 7101 34

28 Urea, Cruise 7102 35

29 Chlorophyll A, Long Island Sound, Cruise 7101 36

iv Figure Page 30 In Vivo Chlorophyll A, Long Island Sound, Cruise 7102 37

31 In Vivo Chlorophyll A Profile, Long Island Sound 38 Cruise 7102 32 Abundance of Urea, Ammonia, Chlorophyll A and 39 Turbidity Measured Between Lower New York Bay and Western Long Island Sound, Cruise 7101 33 Chlorophyll A, Dissolved Oxygen, Salinity and 40 Temperature Measured Between Lower New York Harbor, East River, and Western Long Island Sound, Cruise 7102 34 Temperature-Salinity Correlation and Water Mass Types 42 in Long Island Sound, Cruise 7101 35 Temperature-Salinity Correlation and Water Mass Types 42 in Long Island Sound, Cruise 7102 36 Temperature, Long Island Sound, Cruise 7102 44 37 Temperature Profile, Eastern Long Island Sound, 45 Cruise 7102 38 Temperature Profile, Central Long Island Sound, 46 Cruise 7102 39 Salinity, Cruise 7102 47 40 Salinity Profile, Eastern Long Island Sound, 48 Cruise 7102

41 Salinity Profile, Central Long Island Sound, 49 Cruise 7102 42 Dissolved Oxygen, Cruise 7102 50 43 Dissolved Oxygen Profile, Central Long Island Sound, 51 Cruise 7102 44 Dissolved Oxygen Profile, Central Long Island Sound, 52 Cruise 7102 45 Wind Data 55 46 Percentage Probability of Calm Periods During 56 July and August

47 Tidal Currents in New York Harbor and the East River, 58 Three Hours After Low Tide at the Battery

48 Tidal Excursion With Depth at Three Locations in the 60 East River 49 General Water Circulation in the East River 61

r-----~----~----1r----~-----L----_r-----i----~-----.------L-----~----~--~,41°30·

...~ ... 25M~· "· · "···" ·"·L~"" ·· ·

...... 25M r.-..... :: ......

41°00'

I-'

KILOMETERS o !SO , ----,---- 1 o ~ STATUTE MILES

--7..L..2-0--~J'40030' 74° 730 Fig . 1 . Geographic features of Long Island Sound .

A. Rikers Island 1. Housatonic River Q . Stamford , Conn . B. Throgs Neck J . New Haven Harbor R. Mattituck C. Execution Rock K. Connecticut River S . Shoreham D. Hempstead Harbor L . The Race T . Roanoke Point E. Matinicock Point M. Block Island Sound U. Area of Sill Depth F. Eatons Neck N. East River Maximum (24 m) G. Cable & Anchor Reef O. Hell Gate V. Long Sand Shoal H. Port Jefferson P . Smithtown Bay W. Six Mile Reef 74'00' ·w

Na.. t icol Miles . ....' .

I( i lom@~~ oL

45'I, I 'Ib:',' .) , /:.:: \,1 I I :'(1 . rL_u~ml"\;J 1.1 45'

.. "Y''l _" ~ . . V;.r -:(J~~...... "-">"\ ;//1¥f.c!~'f\ IA. STATEN . ·D~~ .> ":' .. V ~'?'~ , ~ eA · 8. t:) t:I C. ISLAND o ::0 ~ :. ~. '.., ~ ""'1J '" ..

B N ~

3If 30' My + +

74'00' 45'

Fig . 2 . Geographic features of New York Harbor and East River. A. Upper Bay G. Rikers Island N. to Raritan Bay B. Lower Bay H. Whitestone Bridge O. Norton Point C. Narrows I. Throgs Neck t· Sewage Treatment- D. The Battery J . Little Neck Bay Secondary E . Hudson River K. Hewlett Point F . Hell Gate L. Execution Rock M. to Sandy Hook Bay 2 r-----~----~----._----~-----L----_r-----L----~-----.------L-----~----~-----141°30·

.30 32 !~_~_3~~ 31 _ ~ ...... -- __ r c:? ., 3.6 37· 26 --- 28 - -..- • .27 41·00'

KILOMETERS o SO I , I " I ' o 30 STATUTE MILES

L-----__r- ____-,r- ____~ ______.------~------L------r------Ir------~------,------.------L-----~1 40°30' 74° 73· 720

Fi g . 3. Station locations of Cruise 7101 , 6- 16 April 1971 . The line shows the location of profiles . 18 • • 19 41 ° I . j j .20 o 10 NAUTICAL MILES

50'

40'

400301 +

82• 40° 74° 50' 40' 73°30'

Fig. 4 . Station locations of Cruise 7101, New York Harbor and East River .

4 ""40°50. NEW ROCHELLE WESTCHESTER

tIO -5 ° ~

() EXECUTION (iJ ROCK < ~ ...... ;) - r,"

NECK

73°50.

/ 40°50. • SEWAGE TREATMENT SECONDARY ~ 1 o 2 3

Fj.g . 5 . Station locati ons of Cruise 710701 , 1 July 1971 . r----L.-- --'------,.----'---.L.----r----'------lL----,----...L-----'-----,------,,41°30·

CRUISE 7102 9-21 AUGUST 1971

\ \ 16\. ,38 "7 \ , 8 '"

KILOMETERS o ! oI ~i ? 740 73. STATUTE MILES 30 I 400 30' 720

Fig . 6 . Station locations of Cruise 7102 , 9- 21 August 1971 . The line shows ' p r ofil e l ocati ons . o 5 10 , • , , I I, , l STATUTE MILES o 10 " , , I , KILOMETERS

41°1 . j

40030' .58 + ~7

. . l I FI 40° ' 740 73030'

Fi g . 7. Station locations of Cruise 7102 , 9- 21 August 1971 , New York Harbor and East River .

7 INTRODUCTION

The Marine Sciences Research Center (MSRC), State University of New York at St ony Brook, conducted oceanographic cruises during April (Cruise 7101) and August (Cruise 7102) of 1971. The cruise s surveyed Long Island Sound, East River, New York Harbor, New York Bight, and Block Island Sound. This report considers hydrographic features of Block Island Sound, Long Island Sound, East River, and New York Harbor. Comparable features of the New York Bight and adjoining slope water are reported elsewhere (Bowman and Weyl, 1972).

Cruise 7101 (Fig. 3) took place during 9-12 April and 15-16 April, a period coinciding with seasonal spring runoff when river discharge into Long Island Sound and adjacent areas is at a maximum. Cruise 7102 (Figs. 6,7) conducted during 9-14 and lS August, surveyed the same area as the April cruise. August is a period of maximum water temperatures, when stratification of the water column is usually most pronounced. A brief cruise in July (Cruise 710701, Fig. 5) on the MSRC's R/V MICMAC, consisting of five stations between Execution Rock and Stony Point in the East River, is included b e cau s e it provides supplementary physical data prior to Cruise 7102.

ACKNOWLEDGEMENTS

Cruises 7101 and 7102 we r e conducted aboard R/V UNDAUNTED operated by the Cape Fear Technical Institute, Wilmington, N.C. Appreciation is expressed to James Smith and Capt. Jordan, acting for this institution, for their assistance in planning and scheduling these cruises. Chief Scientists were P. K. Weyl for Cruise 7101 and M. Grant Gross for Cruise 7102.

Faculty members and students from many institutions contributed their time and energy toward the scientific data collection and sampling: State University of New York (Binghamton, Oswe go, Maritime Colle g e at Fort Schuyler, Suffolk County Community College, Stony Brook), Adelphi University, C. W. Post College of Long Island University, Lamont-Doherty Geological Obse rvatory of Columbia University, Boston University, and Massachusetts Institute of Technology.

William Loeffler, Paul Moskowitz and David Jay assisted with data analysis. Diagrams and graphs we re completed by Karen Henrickson, Marie Shanahan and Marie Eisel. Preparation and construction of the instrumentation for the cruise were assisted by Glen Hulse and Michael Scheffler. Nutrient analysis for Cruise 7101 was performed by Gle n Hulse and for Cruise 7102 by yu-jean Liang and Paul Lin.

This report was prepared with support from the Nassau-Suffolk Regional Planning Board, under the direction of M. Grant Gross, with suggestions and criticism from M. Grant Gross and P. K. Weyl.

Financial support for the cruises and data reduction was provided by Grant EP 0039S-02, Solid waste Research Division, Environmental Protection Agency, and Office of Naval Research Contract No. N00014-6S-C-029S.

S .~LING AND ANALYTICAL TECHNIQUES

A shipboard s e awater analysis system was installed aboard R/V UNDAUNTED at Wilmington, N.C. at the commencement of Cruises 7101 and 7102. The system was tested en route between Cape Fear, N.C. and Cape May, N.J.

The major components of the water analysis system consisted of a submersible pump, a through-the-hull seawater intake at a depth of 3.3 m, and an instrument

B module. A thermistor was placed into the ship seawater intake for the purpose of recording surface temperature (3.3 m depth) while cruising between stations. Both the submersible pump and the hull seawater intake were connected independently to the instrument module. The submersible pump system operated only during vertical sampling at hydrographic stations and was isolated from the hull seawater intake system by shut-off valves. During Cruise 7101 this arrangement permitted the continuous strip chart recording of temperature and turbidity and allowed periodic manual readings of conductivity and dissolved oxygen. water samples for chemical analyses were filtered from the sample stream flow through a Reeve-Angel Gamma 12 filter tube (8 micron pore diameter) and immediately frozen.

During Cruise 7101, turbidity was monitored using right-angle scatter or nepthelometry in a continuous-flow fluorometer (stephens, 1967). A primary filter, Corning 7-60 (maximum transmission at 380 nanometers), and a secondary filter, Corning 5-60 (maximum transmission 515 nm), were used with an F4T5 blue fluorescent light source.

Modifications to the system permitted salinity, dissolved oxygen, temperatu~ and in-vivo chlorophyll to be recorded continuously during Cruise 7102. A Bisse~erman 6600T salinograph permitted continuous and direct recording of salinity. Comparison of salinity values obtained between the salinograph and a Bissett-Berman 6230 salinometer showed a maximum variance in identical sample readings of ±0.03 ppt.

In-vivo chlorophyll A was measured fluorometrically during Cruise 7102, according to the method of Lorenzen (1966). Calibration of fluorometer readings was achieved by drawing samples from the fluorometer seawater outflow and spectro photometrically measuring the acetone-soluble filtrate according to the method of strickland and Parsons (1968), using UNESCO equations.

Nutrients analyzed during Cruise 7101 and 7102 included ammonia (Solorzano, 1969), orthophosphate (Murphy and Riley, 1962), and urea (McCarthy, 1970). The method of Solorzano was used for ammonia determinations because it is more specific towards the determination of ammonia than that of Richards and Kletsch (1964) used in previous MSRC cruises, and was necessary for the analysis of urea.

WATER TEMPERATURE

Water temperature in Long Island Sound in April 1971 (Figs. 8, 9) ranged from a maximum surface value of 6.2 C at the mouth of the Housatonic River to a minimum value of 3.1 C in bottom water of the Central Basin, north of Smithtown Bay, N.Y. Maximum surface temperatures for the region considered in this report were found in the lower bays of the New York Harbor complex. Surface temperatures to 7.4 C were recorded in Raritan Bay (Station 85). The surface temperature of upper New York Bay was greater than 6 C (Station 8 was 6.1 C) and the Hudson River surface water, at the Battery (Station 9), had a temperature of 6.3 C.

The waters were well mixed as shown by the general lack of large vertical temperature differences throughout Long Island Sound in April, with the exception of local areas of freshwater discharge (Fig. 9). During a severe northeast gale on 6-7 April 1971, a northeasterly wind blew for 27 hours at velocities above 10 m/sec (20 knots) and for much of this period at velocities in excess of 20 m/sec (40 knots) (Fig. 10). Waves 1.2 to 1.5 m (4 to 5 ft) were recorded at the Execution Rock lighthouse (U.S. Coast Guard). The Long Island Sound survey segment of Cruise 7101 occurred two days after this gale. Mixing caused by winds of gale force is usually sufficient to obliterate vertical stratification.

In central Long Island Sound a 3.5 C temperature contour (Fig. 9) defines the boundary of a lens of cold bottom water. The temperature of this cold water mass shows a seasonal lag relative to surrounding waters, so that this winter-formed water persists into the summer (Fig. 12; and Hardy, 1970, p. 18). It is contained within a basin bounded on the west by the Hempstead Sill and on the east by the Mattituck Sill (Fig. 1). Based on salt balance calculations, non-tidal transport in the Central Basin has been found to be significantly lower than in other areas of Long Island Sound (Riley, et aI, 1956). The seasonal lag in temperature of

9 r-----~-----L----~----~------L-----r_----~-----L-----.------L-----~----~-----i41°30i

TEMPERATURE rC)-IM CRUISE 7101 9 - 12 APR IL 1971

~~V.j .~ -4J· ~d • ~.8 c7 \ . • •~.3 4 ~____ 3.8

• 41°00'

I-' o

KILOMETERS o ~ I , ' 'i o ~ STATUTE MILES

~------r-----~r-----~------~------~------~------r------r------~------,------.------~----~I40°30' 14° 73· 12°

Fig . 8. Surface temperat ure (1 m) , Cruise 7101, 9- 12 April 1971 . STATION NUMBER RIKERS EXECUTION STRATFORD THE ISLAND ROCK SHOALS ,RACE 12 13 14 15 16 17 18 21 23 26 29 31 32 33 34 35 5.7 52 4.0 .4.3_ ·4.0 5.0 / --- .4.9. 4.5 . ...- '" 4 .0 ./" -."'\ 10 ",,-- - ...... --. ... '" /' 3.4 \ ...... /'/' \ ..... , ,.3.5 \ 4 .0 \\ 20 .3.4 .. - \ \ .3.5 .3.Z \

I-' :J: 40 I-' ...... a.. w o 50 CRUISE 7101 9-12 APRIL 1971 TEMPERATURE COC)

o 5 10

STATUTE MILES 70 . 5 10 15 , , l KILOMETERS

80~'~------______..J

Fig . 9. Temperature profile, Cruise 7101 , 9- 12 April 1971 . Table 1 . Estimated Stream Discharge to Long Island Sound , 1970- 1971 (U . S . Geological Survey)

c Connecticut River Housatonic River Hudson River Month b 3 cfsa m3/sec cfs m3/sec cfs m /sec

October 8 , 080 229 2 , 160 61 10 , 800 306 November 8 ,720 247 1,960 56 16 , 800 476 December 17 , 200 487 5 , 560 157 15 , 000 425 January 8 , 000 226 1 , 520 43 12 , 100 343 February 10 , 900 309 2 , 440 69 24 , 100 682 March 20 , 600 583 6 , 790 193 42 , 700 1 , 209 April 46,600 1,320 6 , 250 177 50 , 100 1 , 419 r~ay 45 , 600 1,291 5 , 110 145 44 , 800 1 , 269 June 8 , 630 244 1 , 570 44 10 , 400 294 July 4,310 122 740 21 6 , 980 198 August 6 , 580 186 850 24 13 , 400 379 September 7 , 740 219 3, 290 93 18 , 300 518

Mean Annual 16 , 100 456 3 , 190 90 22 ,100 626 acfs--cubic feet per second bm3sec-- cubic meters per second CTotal discharge ; volume of water of Hudson River origin discharging into Long Island Sound not determined .

Table 2 . Water Temperature , Salinity , Density and Dissolved Oxygen Concentrations in Western Long Island Sound , 1 July 1971 , Cruise 710701

Temp . Station Depth Time Latitude Longitude Salinity Density °2 (meters) EST %0 ppm °C

1 1 1245 40 052.6 ' N 73°44.7 ' W 19.3 25.19 17.51 7.1 12 14 . 6 25 . 74 18 . 97 3 . 4 2 1 1310 40 0 49 . 5 ' N 73°46 . 6 ' w 18 . 7 24 . 57 17 . 18 4.6 6 18 . 7 25 . 47 17.87 3 . 7

3 1 1350 40048 . 2 ' N 73° 49 . 9 ' \oJ 20 . 1 23 . 80 16 . 01 3.4 10 19 . 5 23 . 86 18 . 46 3 . 5 4 1 1515 40 047 . 6 ' N 73° 51. 8 ' W 20 . 3 23 . 56 16 . 03 2 . 7 10 20 . 3 23 . 89 16 . 28 2 . 7

5 1 1540 40° 47 . 4 ' ~J 73°55 . 1 ' W 21. 7 22 . 25 14 . 64 1.3 15 21.6 22.25 14.72 1.7

12 I CRUISE PERIOD I

24 1 (I I ., !, -I (d It d I I I . . WIND VELOCITY DIRECTION en 21 FROM -a::: CALM ::::> 18 o o { [TI ------EAST :I: 15 3 .6- 7.7 M/SEC. ~ ------WEST - 12 Z 9 [] -. ------EAST I-' o 7.7 -10.3 M/SEC. { W «~ 6 ~ ------WEST a::: 3 • ------EAST ::::> ( 10.3 M/SEC. { o G ------WEST MARCH APRIL 1971

Fig . 10 . Wind data at Execution Rock , N. Y. r--....L.---.L.---r---.L...---"----r---l.---L---r----.L.---..L---....------.·41°30· SURFACE TEMPERATURE (OC) - 1M CRUISE 7102 9-12 AUGUST 1971

·.19~ ~ 19.0~8.3

4'·00'

I-' 01:>

KILOMETERS o ~ Ii' " 'i o ~ STATUTE MILES

~------~------~------~------,_------,,------~------_r------_.------~------.r------.------L-----~'40°30' 14° 73° 12°

Fig. 11 . Surface temperature COC , 1 rn) , Cruise 7102 , 9- 12 August 1971 . STATION NUMBER EXECUTION STRATFORD THE SOUTHWEST ROCK SHOALS RACE LEDGE I I 689 10 39 18 35 21 22 23 27 2~ 20-.1 22-.7 21.8 - - 20.0 /\ -/ I -

I ~ £l. 3 ..... W VI o

TEMPERATURE (OC) CRUISE 7102 40 9 -12 AUGUST 1971

o 5 10 15 20 50 I I I ! STATUTE MILES 5 10 15 20

KILOMETERS 60

Fig . 12 . Temperature profile , Cruise 7102 , 9- 12 August 1971 . the Central Basin bottom water is evidence that it mixes slowly with the surrounding water during warmer seasons.

There were three areas of higher surface temperature in Long Island Sound in April (Fig. B), each associated with discharges of the Connecticut and Housatonic River mouths, as well as the East River entrance to Long Island Sound (Fig. 13). While the East River is a tidal strait (Marmer, 1935), freshwater discharged by the Hudson River passes through it. The annual peak river discharge of the Hudson River occurred during April 1971 (Table 1). The refore, maximum diluting effects of this Hudson River component we re experienced during the April cruise.

Temperature measurements on 1 July in western Long Island Sound (Execution Rock) showed the existence of a thermocline with a temperature differential of 4.7 C between 1 m and 12 m (Table 2 and Fig. 5). waters at other stations in the East River were more homogeneous. Highest temperature values were found in the East River (Station 5 was 21.7 C); surface temperatures declined in Long Island Sound. The surface temperature minimum of IB.7 C, at Station 2 north of Great Neck, N.Y., may r e flect mixing with colder bottom water at Execution Rock.

In August 1971 maximum surface tempe ratures of 24 C we re found in central Long Island Sound in an elongated pool of surface water, extending from Smithtown Bay to Mattituck, 5 to 6.5 km (3 to 4 miles) north of the Long Island shore (Fig. 11). In the eastern portion of the Sound, surface temperatures declined to 19 C and lB C in Block Island Sound. Surface wate rs n ear the Connecticut shore were consistently colder than those measured along Long Island. These north-south temperature differences occasionally exceeded 3 C.

Thermal stratification for major areas of Long Island Sound in August was generally ill defined or virtually absent (Fig. 12\ . However, a slight thermo cline was found (in the cruise track profiled) west of Stratford Shoals between Stations 10 and 45. The existence of generally weak temperature stratification in August 1971 was in marked contrast to the pronounced thermocline found in August 1970 (Hardy and Weyl, 1971). The relation of temperature stratification to summer .winds will be discussed later.

SALINITY AND DENSITY

Salinity and density profiles for much of Long Island in April (Cruise 7101 ) were characteristic of a well mixed water column (Figs. 13, 14, 16) . vertical differences in salinity and density existed at the eastern and western e nds of Long Island Sound. The presence of density stratification in these localities is suggestive of the tWO-layered flow which characterizes estuarine circulation (Bowden, 1967). At the eastern end, Block Island s~und wate r, identified by higher salinity (30.0 ppt) and density (1.024 gm/cm ), has a net movement into Long Island Sound where it forms the bottom water (Figs. 14, 16) (Riley, 1952, 1956). A less saline surface layer, representing a mixture of river water and groundwater discharge, moves easterly out of the Sound (Riley, 1956). The Connecticut River, at its seasonal peak (Table 1), discharged a low-salinity pllune which was measured at Stations 32 and 33 (Fig. 14). vertical differences in salinity and density disappear west of the Mattituck Sill (Fig. 1 ) where the Central Basin water is seasonally more homogeneous in physical properties.

The western end of Long Island Sound, in April, also showed a well developed estuarine stratification. At Throgs Neck (station 13) less saline (25 ppt), warmer (5.0 C) and less dense (1.020 gm/cm3 ) water overlays colder (4.5 C), more saline (26.0 ppt) and denser (1.0205 gm/cm3 ) water (Figs. 9, 14, 15, 16). This two-layered structure extended westward from the Hempstead Sill for a distance of 26 km to Hell Gate in the East River where pronounced tidal mixing results in the disappearance of vertical gradients.

In July, vertical salinity and density gradients were present throughout western Long Island Sound and in the East River (Cruise 710701, Table 2). Surface salinity and density decreased progressively from Long Island Sound to the East River. The salinity distribution supports the view that the East River is a source of freshwater for Long Island Sound.

16 41 0 30' I SALI N ITY (%0) - I M CRUISE 7101 9-12 APRIL 1971

~25.0- ~~ ,26.0/ --27.0 ~7. 9 •

I-' -.J

KILOMETERS o ..---' , , ' 50' o i ~,N~=!> "" ~~ STATUTE MILES 30

740 73- 720

Fig. 13. Surface salinity (1 m) , Cruise 7101 , 9- 12 April 1971 . STATION NUMBER RIKERS EXECUTION STRATFORD THE ISLAND ROCK SHOALS RACE 1'2 13 14 15 16 17 19 21 2'3 2p 2,9 3,1 32 33 34 3'5 024.2 025.J /0 026.2 / 027.0 027.9 -ru 0/ I l35.0 / / 28 . 0 ~ /' I • / . I • / 28.10 284. 0 ", /' 0 / 28.5 0 2~8. 8 / ...... --~ ~ o 10~ 0 r 0 0 27.5 25.5 I 27.0 / I 29.0 ! " ~ I 26.5 ...... 0 lV ", I I / ", / o 0 20~ ~ : 0 0 , I"' 1 0 71-0 K" I I \ 027.9 I \ 027.1 027.3 I \ ?:5 30 \. I · • ...- ' :!!

I-' r CD ~ 40 30.30 Q.. W 0

50 CR UISE 7101 9 -12 APRIL 1971 SALINITY (%o) 60

o 5 10 70 STATUTE MILES 5 10 15 I I I KILOMETERS 80~1------______~

Fig , 14 , Salinity profi le , Cr uise 7101 , 9- 12 April 1971. 5

STATION NUMBER NORTON BATTERY HELL GATE RIKERS EXECUTION PT I SILL ISLAND ROCK 86 8 10 " 7 I~ 13 14 15 °t\\\ \\\,,=' ~ 71 I I ! 7 ~72~ . 2 /7' 2L//./ 25 ././ - 25.5./. 20.7 , 26.0 ./ 10 -I \ 'u '\. "'-.., .-r' 7 > 77 )j 5 ~ rY - I " / 26.5

15-1" " \. '" ~ . -" SALINITY (%0) '\1 ~~'/ ~ lJl! I A. "- .,.,~ P!'i7 20

~ I-' - '" ::z::r CL w o ')~6 . B ~6 . 1:::;:::::::"'" ;S.9 - -S.7./ -S.3 -S.2 ./ ./ ./ &0 ./ 51 ~ _S.6 - ./ / - 5.0 - _4.9 -- S.B _4.6 4.5 --:0 10-1 ./ - ././ _4.6 / ./ / 5.5 I / 15-f). / / - TEMPERATURE (OC) I / /1 I 05 I I 1 20i A. -;r.' STATUTE MILES o 5 I I I I I KILOMETERS 25

Pi~ . 15. Temperature and salinitv profiles , East River , Cruise 7101 , April 1971 . STATION NUMBER RIKERS EXECUTION STRATFORD THE ISLAND ROCK SHOALS, RACE 1'2 13 14 15 16 17 19 21 23 26 29 31 32 3.3 3.4 I I I :35 < ~ 19 .1 / . / . ,,- - \ 222 "22.Cl---"'"" --- • I 21.0 -- 2i.7 21~5~ /" - \ . / /20.6 I 20.0 • I • 22....5 • _ ...... "2"2.6 I - - . I 21.0 I 10 • I 21.5 I I 20.5 .21.9 22.0 I 22.0 / I .;. - 20 ' 1 .... , / .22.3 / \ 21.2 21.6. I 23.5 / . \ I \ ~ 30 '---- :::E 23.5 N . 0 I t- 23. .7 a.. 40 24.1 w 0

50 CRUISE 7101 9 - 12 APRIL 1971 DENSITY (dt )

o 5 10 I I , 70 STATUTE MILES 5 10 10 I I I KILOMETERS

80' ' I

Fi~ . 16 . Density profile (sigma- T) , Cruise 7101, 9- 12 April 1971. ~

r-----~------~----~r_-----L------~----~------~------L-----~------~------L-----~----~141°30'

SURFACE SALINITY (%0) - 1M CRUISE 7102 9- 12 AUGUST 1971

IV t-'

KILOMETERS o ~ Ii' 'i o ~ STATUTE MILES

L-----~------._-----L------._----_.------L-----_.------._----~------.------.------~~---J'40030' 740 73- 720

Fi g . 17 . Surface salinity (1 m) , Cruise 7102 , 9- 12 August 1971 . STAT ION NUMBER EXECUTION STRAT FORD THE SOUTHWEST ,ROCK SHOALS RACE LEI;>GE 3 4 5 6 8 9 39 18 35 21 2'2 23 27

2~ . ",/ - 30.1 / - / - - - / 25.5 / 210 270 I / 26.9 . / 30.5 - / - / - 27.6 / I - 2 - -27.5 - - 29.0 - / o 02n 0 / / I / - 28.0 I IOj 0 0 /0 ./ / / I 1(0/ --- o-- o~ - / / 30.0 I f:\.... • _ I - - 28.5 :J / / I I / /\ - I '" - '\ - / - I -;.- ~l I -~ h" 1 /' \ / I ~ '~ 28.4 0- / / "- I I, - / ~ 30~ " )(' ·~. 9/ t\ f ~27·1 F / N '1- -/ N W / Q , . I .' SALINITY (%0) CRUISE 7102 ;\ I - - 40~ ~ ~ "k 9 - 12 AUGUST 1971

o 5 10 15 20 STATUTE MILES 5 10 15 20

KILOMETERS 6

Fi~ . 18 . Salinity profile , Cruise 7102 , 9- 1 2 August 1971 . STATION NUMBER EXECUTION STRATFORD THE SOUTHWEST ROCK SHOALS RACE LEDGE

I ~ 4!?oT J ~ ._J »'P ( ("',.~ > 13,1~ ~§,46 3,9 .~ _'~ ~5 j ,2,1 ,~2 ~3) J ~7

/. / / • • 10 I I • I •

• • I 20 • I· • ·21.5 -~ I I I t- I • a.. 30 IV w DENSITY (O""t) I W o CRUISE 7102 9-13 AUGUST 1971 21.4./ • I 40 I I / / 5 ? 1 If Ip 2p / STATUTE MILES r If Ip 2p KILOMETERS 60

Fig. 19. Density profile (sigma- T) , Cruise 7102 , 9- 13 August 1971 . The vertical salinity structure of Long Island Sound in August (Fig. 18) showed weak stratification in western and central areas with vertical differences never exceeding 1.5 ppt. Surface salinities ranged from 23 ppt at Rikers Island (upper East River) to more than 30 ppt in Block Island Sound (Fig. 17). A north south salinity difference of 0.8 to 1 ppt existed, with more saline water present along the Connecticut shore.

The salinity of Long Island Sound waters was generally greater in August than in April when the spring runoff from rivers is greatest. July to September 1971 was a period of minimum freshwater discharge to Long Island Sound (Table 1). The presence of low salinity values in the East River demonstrates the importance of Hudson River discharges in lowering the salinity of waters in western Long Island Sound.

The vertical density structure (Fig. 19) reveals that the maximum vertical density differences, up to 0.0025 gm/cm3 , occur in the central Basin. Density differences between surface and bottom water diminish towards the eastern end of the Sound where strong tidal currents and an irregular bottom topography encourage vertical turbulence and mixing.

Despite strong tidal currents and mixing in the upper East River, a density stratification pe rsisted because of the eastward flow of less dense surface water, and the westward flow of bottom 'water of greater density.

DISSOLVED OXYGEN

Surface waters throughout Long Island Sound were well oxygenated in April (Fig. 20). Supersaturated surface waters were present throughout the water column from the East River to Long Island Sound. Three stations in upper New York Bay were undersaturated (Stations 8, 9, 10). However, these stations generally exceeded 80 percent of saturation from surface to bottom.

In July 1971, dissolved oxygen concentrations were low; the surface concen tration at Station 1 (Table 2) failed to satisfy the minimum water quality criteria established by the Interstate Sanitation Commission (1971). Surface dissolved oxygen values ranged from 7.1 ppm to 1.3 ppm and bottom concentrations from 3.7 ppm to 1.7 ppm. Dissolved oxygen concentrations generally decreased from east to west.

During August 1971, the dissolved oxygen concentrations in western Long Island Sound exceeded those measured during August 1970 (Hardy and weyl, 1971). The r e lationship of dissolved oxygen and thermocline structure to summer winds will be discussed in a later section.

A continuous zone of low dissolved oxygen levels (less than 4.0 ppm) existed, below a depth of 7 to 8 m, west of Stratford Shoals and continued into the East River (Fig. 22). Low dissolved oxygen concentrations of less than 3.0 ppm from surface to bottom were characteristic of the East River (Figs. 21, 22, 33, 42).

Surface dissolved oxygen values for western Long Island Sound and along the Connecticut shore were typically undersaturated; small areas of supersaturation were associated with high chlorophyll values (Fig. 30). East and west of the Mattituck Sill a surface layer was distinguishable where dissolved oxygen levels exceeded 7 ppm. This supe rsaturated surface layer mainly exists south of a longi tudinal axis through Long Island Sound and appears to be closely related to high chlorophyll value s (Fig. 30).

24 r-----~-----L----~----~------L-----~----~-----L-----.------L-----~----~----~141°30·

O2 (ppm) - 1M CRUISE 7/01 9-12 APRIL 1971

13.6• • \ • • 13 • ~5 12.3

lJl'"

KILOMETERS o ~ I i" i o ~ STATUTE MILES

~------r-----~~----~------~------~------~------>r------>r------~------,------,------~-----J'40030' 740 73- 720

Fif. . 20 . Surface dissolved oxygen (1 m) , Cruise 7101 , 9- 12 April 1971 . 41°30' DISSOLVED OXYGEN (PPM) - 1M CRUISE 7102 9 - 12 AUGUST 1971

•8.0 ~ .8.3 d .8.6 c:7 IO~ (

41°00'

N '"

KILOMETERS o , oI ~i 30 STATUTE MILES

74° 73·

Fir;. 21 . Surface dissolved oxygen profile (ppm) , Cruise 7102 , 9- 13 August 1971 . •

STATION NUMBER EXECUTION STRATFORD THE SOUTHWEST ROCK SHOALS ,RACE LEDGE, 39 18 35 21 22 23 27 I I I I I ·7.5 ·8.6 I~g :..1 · · / • 8..7 . • ~ \ - \ - .2.7 ,;5.0 • I I .• - 1\ \.- \ \ \ ..- e • 10~ • 3fl • • •

1.~2. • .z.-' I .\ - \ \ \ ~ • • • 20 2 .~ • • •

•

~ • 30 • IV DISSOLVED OXYGEN (PPM)~ I -..J I- a.. CRUISE 7102 w 9 -13 AUGUST 1971 0 • 'i \ 8.4 • 4

50 9 ~ Ip ',5 20 STATUTE MILES 5 10 15 20 I I I I KILOMETERS 60

Fig . 22. Di s solved Oxygen Profile , Cruise 7102 , 9- 13 August 1971 . REACTIVE PHOSPHATE

Reactive phosphate concentrations (Fig. 23) in surface waters in April ranged from a minimum of 0.4 uM/l in Block Island Sound to a maximum of 5.3 uM/l at Rikers Island. Orthophosphate concentrations in excess of 2 uM/l were commonly associated with waters adjacent to the New York metropolitan area which includes New York Harbor, East River, and western Long Island Sound as far as Matinicock Point. Concentrations of orthophosphate in surface waters from upper New York Bay and in the East River to Execution Rock (Stations 86, 8, 10, 12, 13, 14) were greater than bottom layer orthophosphate concentrations by a mean difference of 0.48 uM/l. Increased concentration of orthophosphate at the surface existed despite active tidal mixing. Abundance of orthophosphate in surface waters indi cates the presence of nutrient-containing low-salinity effluents (municipal sewage, industrial discharge) discharged into the East River. Elsewhere in Long Island Sound, a vertical concentration gradient for nutrients was absent or failed to show a consistent trend.

In Long Island Sound, orthophosphate concentrations in August (Fig. 24) were generally higher than in April for localized areas. Two stations (18 and 19) had anomalously high concentrations which may be the result of analytical error. Orthophosphate concentrations in the East River remained at high levels similar to those found in April. Orthophosphate was always present in April and August at concentrations adequate to sustain phytoplankton growth: it could not therefore be conside red a limiting nutrient (Ryther and Dunstan, 1971).

AMMONIA

Surface ammonia concentrations in April (Fig. 25) increased from east to west. Concentrations in Block Island Sound were less than 1.5 uM/l. Concentra tions in New York Harbor exceeded 10 uM/l with a peak of 23 uM/l in the East River at Rikers Island.

Ammonia is an important nitrogen source for phytoplankton (Vaccaro, 1963). The variability in surface ammonia during April probably reflects nutrient depletkn caused by phytoplankton "blooms". In Long Island Sound, a winter bloom usually commences between late February and mid-March (Riley, 1956; Hardy, 1970, Hardy and weyl, 1970). The bloom continues until all soluble inorganic nitrogen sources (NH3' N02, N03) are essentially depleted. The inverse relation between chlorophyll and dissolved nitrogen fractions during the spring phytoplankton bloom has pre viously b een demonstrated in western Long Island Sound (Hardy and Weyl, 1970, pp. 44- 49). Low ammonia concentrations in surface waters between Matinicock point and Smithtown Bay can be explained as a result of uptake by phytoplankton. The presence of a surface ammonia concentration of 4.4 uM/l near the mouth of the Housatonic River, where the concentration at 8 m was 2.0 uM/ l, indicates an ammonia input by the freshwater discharge.

Ammonia values in surface waters of New York Harbor, the East River, and the westernmost portion of Long Island Sound are unusually high when compared to surface waters in the New York Bight (usually less than 1 uM/l) or over most of Long Island Sound (less than 3 uM-N/l). The importance of an urban area as an ammonia source is graphically demonstrated in Fig. 32, which represents the results of a continuous sampling during a two and one-half hour passage from Staten Island to Oyster Bay Harbor (Buoy 15) on 16 April 1971. Stations between Sandy Hook and Staten Island were taken on the previous day. Ammonia concentra tions increased markedly between Sandy Hook and the Narrows and between Execution Rock and Throgs Neck. They continued to increase in the East River, reaching a maximum value of over 30 uM-N/l in the upper East River near the sewage outfalls of four secondary treatment plants which discharge 43 percent of the waste of the New York City sewage system (Interstate Sanitation commission, 1971).

Maximum concentrations for all dissolved nutrients analyzed during August were found in New York Harbor. Nutrient levels decreased abruptly away from the immediate effects of the urban areas, and more gradually at greater distances east and south of New York City (Figs. 24, 26, 28).

28 ~

r--L----L-----r---1---....L....--r------.JL----L----r----L---~--_.__--,41°30·

REACTIVE PHOSPHATE (fLM P04 - PI I) - / M CRUISE 7101 9 -/2 APRIL /971 I ·0.5 • .~ • I d c7 •

41°00'

\0'"

KILOMETERS o !SO I 1 " i , i o ~ STATUTE MILES

____ 140° 720 30' 74° 73°

Fig . 23 . Reactive phosphate (l m) , Cruise 7101 , 9- 12 April 1971. 41°30' I REACTIVE PHOSPHATE (,LLM P04 -P/L) - 1M CRUISE 7102 9-12 AUGUST 1971

• • 0.7 ., • .0.9 c7 0.6• • • • ·1.6

41°00'

w o

KILOMETERS o ! ~ o1 ~i 30 ..,~~o::.r__ ?~.c=;;;-,,~ STATUTE MILES

74° 73· 72°

Fip;. 24 . Reactive phosphate (1 m) , Crui se 7102 , 9- 12 August 1971. r-----~----~------r_----~-----L----_.------L-----~-----.------~----J------,41°30'

AMMONIA (,uM NH 3 -N/L) -I M CRUISE 7101 9-12 APRIL 1971

• 214• • 11/ c7

W t-'

KILOMETERS o ~ I i'" o ~ STATUTE MILES

74° 72°

Fig . 25 . Ammonia (1 m) , Cruise 7101 , 9- 12 April 1971 . 41°30'

AMMONIA (,uM NH 3 -N/L) 1M CRUISE 7102 9-12 AUGUST 1971

'04 01.2 !II o )\.... } c7 -05 I •0.1 1.0 1.9 o /(•QO

w IV

KILOMETERS

c=> o oI • i /1 co V c:;> .c:::=:;:. ~ V' POI1 30 ,c:=:: ? ~ STATUTE MILES

400 30' 740 73· 720

Fi g . 26. Ammonia (1 m) , Cruise 7102, 9- 12 August 1971 . Ammonia was present at low concentrations throughout the major portion of Long Island Sound and the New York Bight. certain localized areas such as Smithtown Bay and Hempstead Harbor entrances showed higher ammonia concentrations (Fig. 26).

UREA

During April 1971, urea concentration was measured to identify specific nitrogen sources in the New york area. Urea concentrations measured in the East River exceeded 6 ug-at-N/l with maximum values occurring in the lower East River. For comparison, a urea maximum of 3.07 ug-at-N/l (Newell, 1967) has been reported for the English Channel. vertical stratification in urea concentrations occurs in New York Harbor; there urea concentrations in bottom waters were consistently higher than in surface waters. Urea values rapidly declined to trace amounts in the New York Bight and in Long Island Sound (Figs. 27, 32). Only one small area of Long Island Sound between Stamford, Conn. and the Housatonic River had surface waters whose concentrations exceeded 1 ug-at-N/l. The maximum value was 3.3 ug-at-N/l.

The decrease of urea concentrations to trace amounts away from the metro politan area suggests that urea is rapidly broken down to ammonia by microbial decomposition and hydrolysis, or is utilized as a nitrogen source by autotrophs. High urea concentrations appear as a characteristic feature of the East River and New York Harbor and reflect the quality and quantity of sewage, and its treatment, entering these water bodies.

In August, urea concentrations (Fig. 28) were considerably higher than in April (Fig. 27). Maximum concentrations to 25 ug-at urea-Nil were found in the East River. These urea concentrations were much greater than those that have been measured elsewhere (Newell, 1967; McCarthy, 1970; Remson, 1972).

Presence and distribution of urea were measured to assess its potential as a PI nutrient source for autotrophs and as a specific indicator of sewage discharge. Mammals and elasmobranchs excrete urea; smaller amounts are excreted by certain microorganisms in the breakdown of amino acids, purines and pyrimidines (Remson, 1972) and by copepods (Corner and Newell, 1967). Culture experiments have demon strated that some phytoplankton utilize urea as their sole nitrogen source (Guillard, 1963; McCarthy, 1971). Skeletonema costatum, the dominant species of phytoplankton in Long Island Sound (Conover, 1956) can take up urea at concentra tions of less than 1 ug-at urea-N/liter (Mccarthy, 1970). If urea contributed by elasmobranchs, microorganisms, and copepods is small in relation to that released by mammals near heavily populated coastal areas, then the urea distribution indi cates the presence of recently discharged domestic sewage.

CHLOROPHYLL

Chlorophyll A levels'3in April, represent post-bloom conditions (Figs. 29, 32); a maximum value of 30 mg/m occurred near Rikers Island. ~hlorophyll concentratiaoo decreased eastward from Rikers Island to less than 10 mg/m at Matinicock Point and southward to a level of 18 mg/m3 at the Battery. • There was a vertical gradient in chlorophyll concentrations in upper New York Harbor (Stations 8, 9), where surface values for chlorophyll A were one-fifth to one-third that of the bottom water. The lower surface chlorophyll values were associated with low salinity values.

Highest chlorophyll values were recorded in Raritan Bay (Stations 84, 85) where chlorophyll concentrations ranged from 58 to 100 mg/m3 • The temperature and sali nity characteristics of Raritan Bay water (temperature ranged from 7.1 to 7.4 C and salinities 18 to 21 ppt)hydrographically distinguish it from New York Harbor and the Sandy Hook Channel. Nutrients appeared exhausted at Station 85 where ammonia was 1 uM/l and orthophosphate levels were less than 0.05 uM/1.

33 r-----~----~----_r----~----~~----r_----~-----L-----r----~~----~----~-----141°30'

UREA (fLg - at UREA - Nil ) - 1M CRU ISE 7101 9 - 12 APRIL 1971

.. ~ • 0.0 0.3 • • 0.0 ., 0.6 0.5 C1'

• • 0.1 0.3

w "'"

KILOMETERS o ~ Ii' 'i o ~ STATUTE MILES

~------~------r------~------r------'------~------~------r------~------~------,~------4-----~140030' 740 73° 72°

Fig. 27. Urea (1 m), Cruise 7101, 9- 12 Aori1 1971 . r-----~-----L----~r_----~----~----~------L-----~-----r------L-----~------,41·30' UREA (p.g-at UREA Nil) - 1M CRUISE 7102 9-12 AUGUST 1971

d • c7 • • 12 • I • • ~~. • 41·00' -~~ w lJ1

KILOMETERS ~ 0. o ~ ~ I ii'i 4_ PQI)rJ~V~ o ~ ...... -:> STATUTE MILES

L-_____,.------.------L------~-----,r_-----L------>r------._----~~-----.------.------~~--~'40° 30' 74· 73- 720

Fig. 28 . Urea (1 m), Cruise 7102, 9- 12 August 1971 . r-----~L-----~------_r------i------~----~------L------~------r-----~L-----~------~------141 °30' CHLOROPHYLL A (MG/M3 ) -1M CRUISE 7101 9-12 APRIL 1971

• • III •Io.f c7

• •

w '"

KILOMETERS o ~ I iii" , o ~ STATUTE MILES

~------~------~------~------'------~------~------r------~------~------~~------r------~----~'40°30' 74° 73· 72°

Fig . 2 9 . Chlorophyll A (1 m) , Long Island Sound , Cruise 7101 , 9- 12 April 1971 . r-----~----~----._----~-----L----_r----~----~-----,------L-----L-----~-----,4'030' IN VIVO CHLOROPHYLL A (MG/M3) - 1M CRUISE 7102 9-12 AUGUST 1971

,05.1 ~ ' .... ~0,

d 7.39 0 I I ~.9 I

4,000'

W -..J

KILOMETERS o ~ Ii' " o ~ STATUTE MILES

~------~------~------~------'------~------~------r------~------~------~r------~------L-----~'40°30' 74° 73· 72°

Fig. 30 . In vivo chlorophyll A (1 m) , Long Island Sound , Cruise 7102 , 9- 12 August 1971 . STATION NUMBER EXECUTION STRATFORD THE SOUTHWEST ROCK SHOALS RACE LEDGE I I I I 3 4505 6 8 9 10 39 18 35 21 22 2328 27 • 13.5• ·7.5 • 7•.3 4•.7 • .8.8 .8.0 • • • • 4.3 10,. • • 7.6 • • 7.1 • • • • • ·7.6 5

• 2.2•

• -~

I r 0.. IJ..J w Q CD

3 CHLOROPHYLL A (MG/M ) CRUISE 7102 9-12 AUGUST 1971

5 o 10 15 o STATUTE MILES 5 10 15 20

KILOME TERS 6

Fig . 31. In vivo chlorophyll A profile, Long Island Sound , Cruise 7102, 9-12 August 1971. NEW YORK HARBOR II EAST RIVER II WESTERN L. I. S. ISANDY THE BATTERY TRIBOROUGH THROGS EXECUTION MATINICOCK OYSTER HOOK CHANNEL NARROWS NECK ,ROCK ,POINT ,BAY

120 / --0.... o TURBIDITY (FLUOROMETER UNITS) 30 / ' / ' 110 / " x UREA (fLG -AT Nil) I / '" ' ;I ' ...... II AMMONIA (fLG - AT Nil) 100 3 / o CHLOROPHYLL A (MG / M ) / 40 / 90 Q.. / / en "'-, / I- 80 / 20 / II Z "'- / ~ "'- / 70 y/ ---0-...... 30 0:: ..- , ..... '"::E W ..- "\ Z I- / "'- II ...... / (!) W 60 / ::E "'- ~ ::E 0

Fig . 32 . Abundance of urea , ammonia , chlorophyll A and turbidity measured between lower New York Bay and western Long Island Sound, Cruise 7101 , 16 April 1971 . ---NEW YORK HARBOR EAST RI VER ----+---- WESTERN LONG ISLAND SOUND ------

EXECUTION NORTHPORT ROCK POWER PLANT

24+30 _40 '"::;; 15 29 " ::;; ::;; a. ~ .P :::l >- I- . a:: 0 w z ~-, o ". ",' ' _--6------Il--- w ~22 26~ -~ :J w en . , o I- \...... /~/ en I ...... ; ,;(/ en 25 .... "r '~/'<..-" ::::';~"" ~;"I o ,/'___ "-" ..... __ / I • CHLOROPHYLL A (MGt M3) 5 ~ . ~ ~ 21 24 ..... __ ...- ...... "'. "fr- ... - I 10 '"~~.,,, / .. • ...... ,,/ X DISSOLVED OXYGEN (PPM) ---- " "X- - . - . -~,< oX- -- 23 . ..;tf ... _ 6 SALINITY ('Yo.) -- -- "'---"" )~-l(-- D TEMPERATURE (·C) -- I ...... ~-tr / 20

Fi~ . 33 . Chlorophyll A, dissolved oxygen , salinity and temperature measured between lower New York Harbor , East River , and western Long Island Sound , Cruise 7102, 18 August 1971 . Surface concentrations of chlorophyll A, in August, increased westward from a minimum of 3.9 mg/m3 in Block Island Sound to a maximum ranging from 30 to 60 mg/m3 between Execution Rock and Hempstead Bay (Fig. 30) . A localized chlorophyll peak appeared in the Central Basin of the Sound where values in excess of 30 mg/m3 were measured north of Shoreham to Roanoke point, N. Y.

A vertical profile of in-vivo chlorophyll concentrations (Fig. 3l) shows that concentration decreases with depth. However, minimum values exceeded 2 mg/m3 throughout the water column. An interesting feature is the increasing depth of the 10 mg/m3 contour line from the surface in central Long Island Sound to a depth of 14 m from Execution Rock to Throgs Neck. In the New York metropolitan area, two chlorophyll A maxima (Fig. 33) occur. The largest maximum, ranging from 30 to 50 mg/m3 , is found between Throgs Neck and Hempstead Harbor. The chlorophyll A values ~apidly descend to levels less than 10 mg/m3 in the East River, rising to 15 mg/m between the Battery and lower New York Harbor, reaching a second maximum of 25 to 30 mg/m3 in Sandy Hook. The occurrence of lower chlorophyll concentra tions in the East River, despite the availability of high concentrations of nutrients, suggests that the standing crop of phytoplankton is reduced where the sewage input is at a maximum.

TURBIDITY

Turbidity values (Fig. 32) are recorded in arbitrary fluorometer units (30X scale). Peak turbidity values occurred in New York Harbor and probably represent suspended matter borne by the Hudson River discharge or resuspended by dredging operations in the New York Harbor area. Turbidity declined to low values in the New York Bight and in Long Island Sound.

WATER MASS TYPES

In Long Island Sound four water types can be identified using temperature salinity data taken during Cruise 7101 in Block Island Sound, Long Island Sound, and the East River (Fig. 34). Points on the temperature-salinity (T-S) diagram represent a relation for each station depth sampled and are shown to cluster in groups of varying areal distribution. Each group of points represents a water mass of similar T-S characteristics. Some stations located at mixing boundaries between two water masses may show a large change in the T-S relation between two contiguous depths. T-S correlations give insights into mixing between waters in or entering Long Island Sound.

The major source of salt water to Long Island Sound is Block Island Sound water (Fig. 34, Type III). This wate mass is distinguished by high salinity (30.0 ppt), high density (1.024 gm/cm3 ), and low temperature (3.8 C). The temperature of this water varied little (3.6 to 3.9 C), either vertically or horizontally.

Two low-salinity water types can be distinguished during the April period of peak river discharge. The East River water (Fig. 34, Type I) is the most prominent; it is characterized by relatively high temperatures and low salinities. This water is derived from the Hudson River, upper New York Bay and Central Basin (Fig. 34, Type II).

Long Island Sound surface water (Fig. 34, Type rv) was evident in the central and eastern areas of Long Island Sound. This water is distinguished by low to intermediate salinities and higher temperatures; it forms surface layers which are most conspicuous near the Housatonic and connecticut Rivers. Long Island Sound surface water represents a low density surface layer, formed by discharges of rivers and streams mixing with Long Island Sound waters. Tidal currents and winds can be expected to highly modify the direction and the spatial configuration of

41 7

EAST RIVER WATER II CENTRAL BASIN WATER III BLOCK ISLAND SOUND WATER ~ 6 1 ------.~ IV LONG ISLAND SOUND SURFACE WATER ~ 5 :) ~ ct: w a.. 4 ~ W '\ ,. ;.~-....~ .. - ... - III ••• I- 3

2~1r-----~-----.----~------~-----r----~------.-----~----~ 23 24 25 26 27 28 29 30 31 32

SALINITY (%0)

Fig . 34 . Temperature- salinity correlation and water mass types in Long Island Sound , Cruise 7101 , April 1971 .

. .. .. lIe ... . • ·...... •. . ~ 21i ~...... W . • . ct: :::> 20 ~ • .. ct: ... . . W a.. .. ~ .• W J \ I-

I EAST RIVER WATER

17 II CENTRAL BASIN WATER m BLOCK ISLAND SOUND WAT ER

16' ., 23 24 25 26 27 28 29 30 31 Fig . 35. Temperature- salinity correlation and water mass types in Long Island Sound , Cruise 7102 , August 19 71 .

42 flow in local areas. This water mass may show seasonal variations as it was not easily identified in the T-S relation of the August cruise (Fig. 35).

Central Basin water (Fig. 34, Type II) is distinguished by intermediate salinities and the lowest temperatures. In April the temperature of this water ranged from 3.1 to 4.1 C showing greater variation than Block Island Sound water. Ce ntral Basin water is formed by mixing of all water types entering Long Island Sound; most of the mixing occurs at the sills on the east and west ends. The easte rn boundary is locate d n e ar the Mattituck Sill where turbulent tidal currents cause mixing of waters from Block Island Sound and the Central Basin.

The western mixing zone exists west of Execution Rock. There, strong tidal currents cause mixing of denser Ce ntral Basin water with easterly-moving less dense East River water. Elsewhere in the Ce ntral Basin, circulation patterns are weake r with vertical mixing d ep e ndent upon win1 mixing. Prolonged periods of calm and g e ntle winds in warmer months promote stratification of Central Basin waters. At such time s the bottom waters are isolated from physical exchange with the surface.

During the warming s e ason, solar h e ating of the surface layer and the result ing partial isolation of surface water by the development of a thermocline results in larger ve rtical tempe rature gradients compared to the narrower vertical distri bution of a we ll mixe d wate r column such as existed in April (Fig. 34) . The August tempe rature-salinity r e lationship (Fig. 35) shows that three water mass type s (as identified from T-S relations in April, Fig. 34) retain distinctive T-S characteristics b e cause each water type has different mechanisms for warming (Fig. 35). East Rive r wate r (Type I) represents the lowest salinity water avail able to Long Island Sound of the four major water masses identified. vertical t empe rature diffe r ences were found to be least because active tidal mixing distri bute s the surface heat input throughout the entire water column. Central Basin wate r (Type II) showe d the largest vertical temperature variation. The seasonally low volume of the rive r discharge and the large local variations in temperature made i t difficult to diffe r e ntiate Long Island Sound surface water (Type IV) which could b e distinguished in April (Fi g. 34). Block Island Sound water (Type III) r e pre sents the most saline water flowing into Long Island Sound. vertical tempera ture diffe r e nce s incre ase we stward toward Long Island Sound as the Block Island Sound water mixes with the warmer water of Long Island Sound. The seasonally lower t empe rature of Block Island Sound water reflects mixing with the rese rvoir of ... cooler ocean water adjacent to Block Island Sound •

THE MATTITUCK SILL

The Mattituck Sill is a submarine ridge which divides Long Island Sound into two basins, the Central and the Easte rn Basin. The ridge extends across Long Island Sound from Northville , N.Y. to Long Sand Shoal, near the connecticut shore (Fig. 1). The ave rage depth of the ridge, from the sea surface, is 19 to 21 m with a maximum of 24 m occurring 9.9 km (6.3 miles) NNW of the Mattituck Inle t. The Central and Eastern Basins have main channel depths which generally exceed 30 m. Thus, the Mattituck Sill interpose s an elevation of 9 m or more to physi cally separate the two basins. Spatial differences in the distribution of salinity, t e mperature , and dissolved oxygen (Cruise 7102) suggest that this ridge limits exchange between the Central Basin and the Eastern Basin.

The eastern margin of the Mattituck Sill is made irregular by the presence of four indentations which penetrate into the ridge but do not breach it. The most northern of the four indentations separates Six Mile Reef from Long Sand Shoal (Fig. 1). The sill depth at the head of the northern indentation, below which direct access to the Central Basin would be blocked by the presence of the ridge, is 21 to 22 m (Coast and Geodetic Survey Chart 1212). This indentation is continuous with the major east-west channel of the Eastern Basin which extends from the Race.

Data collected during cruise 7102 suggest that the major transport of Block Island Sound water towards the Central Basin occurs by way of the northern inden tation of the Mattituck Sill. The horizontal distribution of temperature and salinity at a depth of 25 m (Figs. 36, 39) and in profiles of temperature and

43 r---t..----L--~r----'---...1...--__r---'----.1....-----r--...l..-----...lI.-.----.------.i41°30i TEMPERATURE (OC) 25 M CRUISE 7102 9-13 AUGUST 1971

""" """

t( I LOMETERS o ~ I i" i o ~ STATUTE MILES

~------~------~------~------r------r------~------r------~------~------r------~------~-----J'40°30' 74° 73° 72°

Fig . 36 . Temperature (25 m) , Long Island Sound , Cruise 7102 , 9- 13 August 1971 . ~

A STATION NUMBER AI I I N.Y. 37 36 35 34 33 CONN. ·23.6 .20.1 21 ___

5 • • •

• 10 • " •

15 -~ :t:.... a.. 20 w 0

01'> TEMPERATURE (OC) l.11 CRUISE 7102 " AUGUST 1971

35 2 STATUTE MILES

1 2 3 4 , I , KILOMETERS

Fig . 37. Temperature profile , transect A- A', eastern Long Island Sound, Cruise 7102, 11 August 1971 . STATION NUMBER B B' I I N. Y. 38 39 40 4-' 42 CONN. .22.7

5 .22.7

.22.7

-~ ~ -22 - 15 I ~ Q.. LaJ 0 os:> 2~ ·20.2 t:!1 .21.2 CTI "

o I 2 3 4 !5 I I I , , , STATUTE MILES !5 TEMPERATURE (OC ) KILOMETERS 3~ CRUISE 7102 12 AUGUST 1971

NORTH - SOUTH TRANSECT Fig . 38. Temperature profile , transect B- B', central Long Island Sound , Cruise 7102, 12 August 1971. 1--...I.---L----r-----L---L---,------L----L.--.-----'--~--...... __---.t41°30'

SALIN ITY (%0) - 25 M CRUISE 7102 9-13 AUGUST 1971

41°00'

"'"-.I

I( I LOMETERS o SO I i" i o ~ STATUTE MILES

73- '40°30' 74° 72°

Fig . 39 . Salinity (25 m) , Cruise 7102 , 9- 13 August 1971 . AI A STATION NUMBER 1 I N.Y. 37 36 35 34 33 CONN.

· 27.32 /.27. ~4 .28 . 6~ / \ .28.2~ / / \ / 28.5 5-1 1 . 27. 3~ / .28.74 .29.44 ~28.42 / / "- / 27.5 29.0 • " / / .28.82 10~ A . 27.47/ / I ~ .29.44 / 28.5 / 15 . / 28 / -~ 1 \ ;/ / - / / .28.82 oi'> (X) ~ 20i \27.;/ / SAL I N I TY {%o} / 2~.03 f' 25-1 .\ / ~ ~ CRUISE 7102 II AUGUST 1971 .~---~. I '\ / ftft ft_ I- 30

35 0 I 2 I I , STATUTE MILES

0 I 2 3, I ~_ '\. 4°i I I I ' I. KILOMETERS "

Fig . 40 . Salinity profile, transect A- A' , eastern Long Island Sound, Cruise 7102, 11 August 1971 . 8 8 1 I STATION NUM8ER I N.V. CONN. 38 3p 4.0 4) 42, J -27.2 -27.6 -27.7 7 -28.1 -28.0 I / 51 ~ -27.3 / -27.6 -27.7/ -28.0 / / /' -27.3 ....- _27.7 ..... 27.5 - - -- I~ r-- __ 28.0 -~ ~ ~ \0"'" 0... 20-1 1 _28.2 _28.4 I.&.J C

25 --- --28.5 -- - - -28.6 3 o 234 5 I ,I I I STATUTE MILES 5 SALI NITY (%0) KILOMETERS 35 CRUISE 7102 12 AUGUST 1971

Fig . 41 . Salinity profile , transect B- B ', central Long Island Sound , Cruise 7102 , 12 August 1971 . r-----~----~------r_----~-----L----_.------L------L-----r------L-----~----~----~i41°30· DISSOLVED OXYGEN (PPM) - 25 M CRUISE 7102 9-13 AUGUST 1971

41°00.

U1 o

KILOMETERS o ~ I , ' . i o ~ STATUTE MILES

~------T------r-----~L-----~------,------L------r------r------~------~------.------~~--~I40°30. 74° 73· 72°

Fi~ . 42 . Dissolved oxygen (25 m) , Cruise 7102 , 9-13 August 1971 . A AI I STATION NUMBER I N.Y. 37 36 35 34 33 CONN. 1 1 I • \ .8.S I • (8.0 .7.9 \ I 51 '\ • \ • 8.5 • D . U. • \ I \ / ,/ IO~ ). • • /. .7.9

35 012 I I , STATUTE MILES 2 3 40 KILOMETERS

Fi ~ . 43 . Dissolved oxygen profile , transect A- A', central Long Island Sound , Cruise 7102 , 11 August 1971 . I ~ STATION NUMBER ~ N.Y. 38 39 40 41 42 CONN l I "" x I -7.6 -7.~ 7.2- -6.2 ·~.7

5 -7.7

- -7.6 -~ A 7- :t: ~a. w o U1 N

30 o ~ I I STATUTE MILES

~ DISSOLVED OXYGEN (PPM) KILOMETERS 35 CRUISE 7102 12 AUGUST 1971

Fig. 44. Dissolved oxygen profile, transect B- B', central Long Island Sound , Cruise 7102, 12 August 1971 . salinity from a north-south transect across Long Island Sound immediately east of the Mattituck Sill (transect A-A', Figs. 6, 37, 40) shows colder and more saline bottom water present in the northern indentation than was found in the three sill indentations south of Six Mile Reef. The temperature-salinity relation of this bottom water was clearly associated with Block Island Sound water (Fig. 35, Type III). The data suggest that the northern indentation provides a channel of most direct access to the Central Basin, with least dilution, for Block Island Sound water. Details of the mechanism and periodicity by which this bottom water spills over the sill to enter the Central Basin are not known.

A two-layered transport system can be identified in temperature and salinity profiles of transect A-A' (Figs. 6, 37, 40). A wedge of low-density Long Island Sound surface water (Fig. 35, Type IV), primarily identified by the lower salinity but also by higher temperature, has gradient slopes which deepen toward the Long Island shore. This water has a net eastward flow (Riley, 1956). water 3 to 4 C colder and 2 ppt more saline characterizes the bottom water where temperature and salinity contours slope upwards toward the Connecticut shore (Figs. 37, 40). Coriolis acceleration tends to deflect the westward motion of the bottom water to the right, in this case north.

A small wedge of low-salinity surface water, against the Connecticut shore, represents local freshwater drainage (Fig. 31).

North-south transect profiles of temperature and salinity west of the Mattituck Sill (Fig. 6, transect B-B'; Figs. 38, 41) show a less defined and more shallow sloping of the iso-contour lines. The loss of definition of this surface layer within the Central Basin reflects a general weakening of circulation. Winds could be expected to introduce great variability in the spatial distribution of the surface layer.

water of greatest density, identified by lowest temperatures and highest salinities, accumulated in the deepest portions of the Central Basin (Figs. 38, 41) •

The horizontal distribution of dissolved oxygen, at a depth of 25 m (Fig. 42), shows a decline in concentration from east to west. The dissolved oxygen concen tration of the Eastern Basin exceeded 8 ppm with the exception of the area immediately parallel to the Mattituck Sill. west of the sill, the dissolved oxygen quality of the bottom water (25 m) was significantly lower with concen trations ranging between 6.6 and 4.8 ppm (Fig. 42). The dissolved oxygen quality continued to decrease the length of the Central Basin reaching a minimum concen tration of 2.8 ppm at the westernmost boundary. The vertical distribution of dissolved oxygen was essentially homogenous within the Eastern Basin (transect A-A', Figs. 6, 43) with surface to bottom concentration differences of less than 1 ppm. This reflects the active vertical mixing of the water column as the result of the strong tidal currents moving over the irregular bottom topography. Westward of the Mattituck Sill (transect B-B'), where circulation is weaker and bottom topography more regular, the vertical exchange of dissolved oxygen between surface and lower depths is reduced as indicated by a vertical oxygen gradient of 1 to 3 ppm (Figs. 6, 44).

WIND

A relation between the dissolved oxygen quality of western Long Island Sound and the wind was postulated, based on data obtained in August 1970 (Hardy and Weyl, 1971). However, weather records were not available at that time to relate annual differences or short term changes in dissolved oxygen quality to wind patterns.

Weather and sea-state observations taken every three hours at the Execution Rock Coast Guard Station were obtained for the years 1969 to 1971 (National Climatic Data Center, Asheville, N.C.).

The wind velocity, direction, and duration for July and August of three years (1969 to 1971) was graphically interpreted to reveal annual summer differences in

53 wind patterns (Fig. 45). The graph plots duration of event (at three hour intervals) against day of the month. The eight observations made each day are plotted starting at the lower left hand corner of the first column of each year's graph. The topmost line of the first column represents 2400 hours. For chrono logical continuity the topmost line of the second column represents 0000 hours of the second day, and the observation time proceeds to 2400 hours moving down the column to the bottom. This orderly alternation of the commencement of each obser vation day continues throughout each year graph. Each observation is represented by a code pattern to indicate wind velocity and direction. Wind direction is arbitrarily divided into two categories: east (N to SE) and west (S to NW). The basis for this simplification is that the longitudinal axis of Long Island Sound is orientated east to west and therefore winds from the west and east have the greatest fetch. Wind velocity was coded into four categories based on the Beaufort Scale (Vine and Volkmann, 1950) which relates sea-state conditions for the open ocean to wind velocity. Wind velocities less than 3.6 m/sec (0 to 7 knots) are categorized as calm periods where the sea state is smooth and wind induced vertical mixing of the water column is assumed to be negligible. Wind velocities of 3.6 to 7.7 m/sec (7 to 15 knots) produce a slight to moderate sea, which can be expected to cover shallow mixing of the water column. Wind velocities of 7.7 to 10.3 m/sec (15 to 20 knots) are characterized by rough seas which would cause extensive mixing of the water column. Wind velocities in excess of 10.3 m/sec (20 knots) produce a sea state described as very rough to precipitous. However, the sheltering of Long Island Sound by surrounding land masses prevents the extreme sea conditions observable in the open ocean. Adequate information is presently unavailable to relate the depth of water column mixing achieved by specific combinations of wind velocity, direction, and duration in an enclosed water body. One observation of this relation was made in August 1970 (Hardy and Weyl, 1971) when a northeast storm on 11 August (Fig. 45) had high winds for 24 hours (winds exceeded 20 knots for 6 hours). These winds mixed the water column in western Long Island Sound to a depth of 12 m and caused a marked improvement in dissolved oxygen concentrations to that depth.

Comparison of winds in the summers of 1970 and 1971 (Fig. 45) shows that the summer of 1970 was distinguished by prolonged calms interrupted by brief periods of weak winds with the exception of the northeast storm. Hydrographic observations during the summer of 1970 revealed a pronounced thermocline which isolated the bottom water from exchange with the surface layer, causing low dissolved oxygen levels to exist below 5 m. In the summer of 1971 calms were shorter and the frequency of strong winds was greater than in summer 1970. The temperature struc ture of the water column in the summer of 1970 shows that a thermocline was virtually absent or at most weakly formed. The weak thermocline, higher dissolved oxygen concentrations, and the higher frequency of strong winds during summer 1971 show that vertical mixing of the water column by wind action was more frequent and intense than in 1970. The wind patterns for the summer of 1969 are included to emphasize the annual differences in weather which it is contended affects the frequency and degree of water column mixing.

Summer differences in duration of calms are shown where the percent probabili~ of a calm interval is plotted against duration of calm for the months of July and August of 1969 to 1971 (Fig. 46). The probability of a specified calm duration preceding any moment of time within the month is indicated by the graph. The probability of prolonged periods of calm in 1970 is significantly greater than in 1969 and 1971.

From the available evidence, it appears that the dissolved oxygen concen trations in Long Island Sound are sensitive to climatic conditions which permit or inhibit the mixing of bottom water with the surface layer. Prolonged calm periods promote thermocline formation which, in turn, restricts the dissolved oxygen renewal of bottom waters. Dissolved oxygen concentrations under these conditions become increasingly depleted by biological oxygen demands. The degree of the dissolved oxygen depletion is dependent upon the frequency and duration of calms and the strength and duration of the intervening winds. Winds can disrupt the vertical structure of the water column in a matter of hours, permitting the rapid renewal of dissolved oxygen to the lower layers. This relation of the dissolved oxygen concentration to the physical stability of the water column indi cates that the timing of hydrographic surveys, during the summer, assumes import~e in the assessment of water quality whenever dissolved oxygen is one criterion.

54 ~ (:", .. • -', ... L", : . ,_ 000.. ~, ~ 0°: ., 00 ~~" 0 ~ 0 . ~'. .' O"T'l. '\I. ' _ I , ·: +,0 ~ ." ,~: . .

~ " ',, I ~. ',' f~~l~ ,; ,'. ~ ~~ ",' ~ ~ ~ 5 10 15 20 25 30 5 10 15 20 25 30

JULY 1969 AUGUST 1969

I v WIND VELOCITY DIRECTION ~ ~ ~ , (Meters/Sec.) FROM en ~.!. ..J ~ 0-3.6 0 :.... , I.. ', Z a:::~ , ill ~ ~ 2 w ~ h EJ EAST ~ I 3,6 - 7,7 I- l ,I" , ~ WEST e:!a::: -Z f; I; ( :::J a::: , ~{ [ill] EAST o :::J ''.! 7.7 -10.3 o .'~, ~ WEST :t: ,. ~ :' U1 1\: r<) " . ~ " U1 1 ~ ~ • EAST ~~ ~I;, >10.3 ~ G WEST 5 10 15 20 25 30 I 5 10 15 20 25 30 JULY 1970 AUGUST 1970

I , ~ ~ , - '; !.\ ;~ ~ .~ m " ':1\ I ~ r:.- ~ I , ~ ~ ~li ,~ ~,~ ~ ,,\=~: I " ~~ MI ~1 ~~';'/~~; ~ 5 10 15 20 25 30 5 10 15 2Ci 25 ~

JULY 1971 AUGUST 1971

Fig. 45 . Wind data , July- August , 1969- 1971 . 5QO-r------,------, 400 1969---- I 300 1970 ------1\ 1971 ----- . 200 ~ ,I ~ 10.0 ~ 9.0 -.J 8.0 <[ 7.0 0 6.0 t9 5.0 JULY AUGUST Z \\ 4.0 I I 0 .~ W \.-'I \1 W 3.0 0 \- W \'"1_',\_- ct: 2 .0 " '\ a... \. 'L ___ "="-=\_ _ _ _ _~\ tTl 1L.. ~, 0\ 0 -----, '--, I I >- 1.0 \ I- .9 , .8 1 __ - ---I \ -.J --I .7 \ , CD .6 <[ \ \ CD .5 \ I \ 0 ct: .4 '------1 L,. \ - , a... I 1 I ~ .3 0 1 1 1 I .2 1 1 1 I 1 I I I .1 I o 9 99 DURATION OF CALM (HOURS)

Fi g . 46 . Percentage probability of calm periods during July and Au gust , 1969- 1971. CIRCULATION

The general circulation in Long Island Sound was described by Riley (1952, 1956). Less attention has been directed to water circulation in western Long Island Sound. Riley (1956) estimated by an indirect method that the net flux from the East River into western Long Island Sound was of the order of 1,100 m3/sec. Riley suggested that this eastward net flow originated from New York Harbor. A mechanism for this flow was not described. Calculations by P. K. Weyl (personal communication, 1972) based on current measurements tabulated by Marmer (1935) indicate that Riley's estimate of a net eastward transport from the East River may be too high by an order of magnitude.

It should be noted at this point that the East River is a tidal strait connecting Long Island Sound with upper New York Bay. Each end of the East River is connected by separate seaways to the New York Bight which causes the tidal bulge to arrive at each end of the East River with a different amplitude and phase. High tide is approximately three hours earlier at the Battery than at Throgs Neck. The simultaneous tidal heights of the Battery and Throgs Neck may differ by three feet. The mean tide height at the Battery is 4.1 ft and at Throgs Neck it is 7.0 ft .(ESSA, Tide Tables, 1971). The tidal phase lag at each end of the East River, coupled with differences in tidal ranges, establishes a hydraulic head difference between the ends. The tidally established head generates a hydraulic current through the East River (Marmer, 1935). The timing of this hydraulic flow is such that the flood tide in upper New York Bay sets throughout the length of the East River into Long Island Sound and the ebb tide excursion sets from Long Island Sound to upper New York Bay. It must be remembered that the reference point for flood and ebb flow was arbitrarily taken as New York Harbor. (From the viewpoint of Long Island Sound the flood set from New York Harbor would be considered as an ebb flow in Long Island Sound with a similar converse relation for the New York Harbor ebb flow).

Distinct topographic features moved Marmer (1935) to subdivide the East River into Lower and Upper River areas. The Lower East River is a narrow channel (approximately 450 m (1,500 ft) wide), with an average depth of 12 m (40 ft) (Marmer, 1935); it extends 11.5 km (7.2 miles) from the Battery to Hell Gate (Fig. 2). The northern end of the Lower East River is split by Welfare Island into two channels; the western channel is deeper and most significant for tidal flow. Both the flood and ebb velocities decrease with depth but at all depths the ebb velocity is commonly the greatest (Marmer, 1935). The water column of the Lower East River is thoroughly mixed by the turbulence of the strong tidal currents which is evidenced by the small salinity or temperature variations with depth (Fig. 15). The Lower East River water is the lowest density water in the East River as the result of dilution with the Hudson River (Fig. 15). During flood tide Upper New York Bay water moves northward into the East River from two hours after low water to one hour after high water (U.S. Coast and Geodetic Survey, 1956). Waters from the Hudson River move past the Battery and contribute to the East River flood beginning two hours after low water (Fig. 47 ) . When the flood set in the East River reaches Hell Gate, a second low-salinity addition, of Hudson River origin, is encountered coming from the Harlem River (Fig. 47). The Harlem River is another tidal strait, approximately 9.8 km (6.1 miles ) long, which connects the Hudson River with the East River as well as forming the northern boundary of Manhattan. The East River entrance to the Harlem River is located on the western border of the Hell Gate area, and therefore the Harlem River tidal exchange takes place in the boundary zone separating the Lower and Upper East Rivers. During flood tide (New York Harbor tide reference), the direction of flow in the Harlem River is southward towards the East River, and during the ebb the tidal current is reversed. The tidal flow in the Harlem River is closely in phase with the tide flow of the Upper East River (Marmer, 1935). This phase relation causes the low-salinity input from the Harlem River to be carried into the Upper East River and moved toward Long Island Sound for the entire period of the flood excursion. Tidal height differences between the Hudson River entrance and the East River entrance to the Harlem River cause the tidal current to be dominated by a hydraulic head difference (Haight, 1942). Changes in river height during periods of peak Hudson River discharge could be expected to increase the net southward transport of Harlem River water into the East River.

The Upper East River from Hell Gate to Throgs Neck (11 km) is larger and wider than the Lower East River, and has numerous islands and embayments. Its average depth is less than that of the Lower East River (Marmer, 1935). A deep

57 NAUTICAL MILES o e ! I

~<:) V ,tJ:J '"

...... '" "- ...... '" ,,"-...... '-.. -... " - --" '- , ------,,,, " ------I ~. '. , "- ; . -- - \ >: \

Fig . 47 . Tidal curr ents in New York Harbor and the East River , three hours after low tide at the Battery (Coast and Geodetic Survey , 1956) .

58 (usually greater than 12 m or 40 ft) and relatively wide channel extends the length of the Upper East River, facilitating water movement. The tidal phase lag between Throgs Neck and Hell Gate (Hallets Point) is short (4 to 15 minutes) in comparison to the longer lag of 1.8 hours between the Battery and Hell Gate. Tidal current velocities experienced in the wide Upper East River are less than those encountered in the constricted channels of the Lower East River (Marmer, 1935). The flood tide in the Upper East River (New York Harbor tide reference used) decreases in velocity and duration with depth while the ebb tide increases to strength at mid-depths and decreases more slowly toward the bottom (Marmer, 1935) (Fig. 48). The ebb tide duration increases with depth (Marmer, 1935). This vertical distribution of velocity and duration, demonstrated during the ebb and flood cycle, is characteristic of a two-layered transport system.

The Upper East River and western Long Island Sound exhibit a vertical stratification in salinity, temperature and density (Figs. 9, 14, 15) compatible with a two-layered estuarine circulation and suggested from Marmer's (1935) current measurement data. Iso-contour intervals for salinity, temperature, and density display a deepening gradient slope towards the East River which distinguishes a surface water overlying a more dense bottom water. The presence of this density slope indicates that a net advective bottom flow of Central Basin water (Fig. 34, Type II) moves into the Upper East River to displace the less dense East River water (Fig. 34, Type I) seaward (towards Long Island Sound). Tidally induced mixing between the two layers entrains additional volume of bottom water into the surface flow and generates a replacement counter-current of bottom water. vertical stratification loses identifying physical characteristics in the area surrounding Hell Gate where extreme tidal turbulence produces a homogeneously mixed water column. The tidal mixing of the water column continues throughout the length of the Lower East River. From current measurement data Marmer (1935) found no evi dence of a two-layered transport mechanism such as exists in the Upper East River.

The salt concentration in the East River shows a progressive decline from Long Island Sound to the Battery (Fig. 15) as the result of dilution with fresh water of Hudson River origin. Two areas of freshwater input have been previously noted, the Harlem River tidal exchange introduced into the Hell Gate mixing zone and the Battery where minimum salinity concentrations for the East River are found. Therefore, the Lower East River and the Harlem River must be considered as sources for the low density water required to generate a net surface transport into Long Island Sound from the Upper East River.

A generalized scheme of the tidal circulation in the East River is proposed (Fig. 49) based on the current studies of Marmer (1935) and interpretation of data from Cruises 7101 and 7102.

~,e flood set from Upper New York Bay is seen to carry low-salinity water, entering the Lo~er East River, towards the Upper East River. In phase with this flood excursion is the important input of low-salinity water from the Harlem River at Hell Gate. This water of low density moves into the Upper East River where it is displaced over the more dense Central Basin water, of Long Island Sound origin, to form a surface layer. The strength and duration of the flood current in the ourface layer is greater than that found in the bottom water (Table 2) as both water masses are swept toward Long Island Sound. Thus, the flood excursion of the surface layer toward Long Island Sound exceeds that of the bottom water (Fig. 48).

Tidal current directions are reversed during the ebb stage of the tidal cycle to flow toward Upper New York Bay. The maximum current strength and duration is now found within the bottom layer (Fig. 48). The ebb volume return of water toward Upper New York Bay, thus, shows bias towards the bottom water to maintain the flow volume. Transfer of the tidal excursion maximum from the surface layer during the flood stage to the bottom layer for the ebb results in a net displace ment of surface water toward the flood direction. A net transport of East River water into western Long Island Sound is produced by this mechanism. Continuity of volume for this net volume transfer of East River water is maintained by the counter net transport of Central Basin water into the East River. This replacement current in the bottom layer is generated by eddy mixing with the surface layer and volume additions into the Lower East River amid the turbulence created in Hell Gate (Fig. 49).

Surface flood currents moving easterly from Throgs Neck, in the absence of other forces, are deflected to the right by Coriolis acceleration. This causes the surface transport from Upper East River to flow primarily along Long Island's

59 x x x \ \ X \ I 5t- \ \ I 20 x ~ I I I -a:CI) lAJ lol x ~ \ 40~- lAJ lAJ \ lAJ 2 \ LL 5 \ -:z: 1 r I x - ~ ~ :z: Cl. 60 ~ lAJ Cl. 0'\ - FLOOD 0 c 20 lAJ ---EBB o 80 25. I x THROGS NECK- THROGS NECK - OLD FERRY PT. - HUNT POINT - 30LWILLET.. ..PT. CRYDERS PT. WHITESTONE PT. RIKERS ISLAND 100 r- 0 5 10 0 5 10 0 5 10 15 5 10 10 15 20 TIDAL EXCURSION (NAUTICAL MILES)

Fig. 48 . Tidal excursion wi th depth at three locations in the East River . Tidal excursion is mean velocity times duration of tidal stage (adapted from data of Marmer , 1935) . FLOOD TIDE IN NEW YORK HARBOR

HARLEM RIVER ~-..~ ~ ~ .. ~ ~ ~ ~ ~ EAST RIVER WATER --.. ~ ---. ~ ---:IJ' ~ ~ ~ ~ _--+-~~ __~ __ _ ---"~ ~ ~ ~ ---A'.o7 -=...; CEA'"TRAL BASIN WATER--9' . ~~.--.. -.. -. -. --...... -... ;[///177/J!/7!1'7t.. ~ --'; ~ ...... --... --. -.. ~ LOWER EAST RIVER HELL GATE UPPER EAST RIVER WESTERN LONG ISLAND SOUND

EBB TI DE IN NEW YORK HARBOR

~~.- 0Ci:=+-~+ ..... ~ "f--~ ..-~~ .. ~~~ ~- ~ .....-..-~~4-o4r- - y-- ~ ~ .- -- -~ -- "-="'" -- - -""- --- - ~ - ~ 4-- .--

NET TIDAL TRANSPORT IN EAST RIVER

HARLEM RIVER

~ ~ ~ '4-~ ~ ...... ~ ~ ..... ~ EAST IVER WATER ...... ~ ...-' ~ -- ~ ...... ~ + -+ 4- ...- +- • __ - t.,- - 0(..- -,- -;...'l.- ~J\..- - '= - --t..:;- -- -+- .- x--\:::- ..... -- ~ 4- ~ .-~~~ ~"-"'....-.- ..- ~ IfllTII!!IZllA rIli. _.__ ~ _ __ CENLRAL B~IN WA!!..R ~ LOWER EAST RIVER HELL GATE UPPER EAST RIVER WESTERN LONG ISLAND SOUND

Fig . 49 . General water circulation in the East River .

61 north shore rather than to disperse equally throughout the Sound. Available salinity, temperature and nutrient data (Hardy, 1970; Hardy and Weyl, 1971) suggest that this southerly deflected surface drift can be occasionally identified as far east as Smithtown Bay. The magnitude and structural organization of this easterly directed transport is highly variable and could be expected to be influenced by winds.

Large volumes of sewage plant effluents are discharged directly into the East River, as well as the Hudson River. Important sources of these pollutants are municipal sewage plants, storm runoff and numerous industrial waste outfalls. The dry weather discharge of secondarily treated municipal sewage in the Upper East River alone amounts to 580 million gallons per day which is 43 percent of the average dry weather discharge of the New York City sewage system (Interstate Sanitation Commission, 1971). Data concerning the magnitude and quality of storm runoff and industrial discharges into the East River are not available. These low-salinity waste discharges form effluent plumes on the surface of the East River. There the surface circulation tends to transport these pollutants towards Long Island Sound. Winds cause substantial changes in these average conditions.

62 REFERENCES

Bowden, K. F. 1967. circulation and diffusion, p. 15-36. In: G. Lauf (ed.) Estuaries. American Association Advancement Science. Pub. 83. 757 p.

Bowman, M. J., and P. K. Weyl. 1972. Hydrographic study of the shelf and slope waters of New York Bight. Tech. Rep. No. 16, Mar. Sci. Res. Cent., State Univ. of New York, Stony Brook. 46 p.

Coast & Geodetic Survey. 1956. Tidal Current Charts, New York Harbor, 7th ed. ESSA, Rockville, Maryland. 12 charts.

Conover, S. A. M. 1956. Phytoplankton. Bull. Bingham Oceanogr. ColI. 15:62-112.

Corner, E. D. S.,and B. S. Newell. 1967. On the nutrition and metabolism of zooplankton. J. Mar. BioI Ass. U.K. 47:113-120.

Guillard, R. R. L. 1963. Organic sources of nitrogen for marine centric diatoms, p. 93-104. In: C. H. Oppenheimer (ed.) Marine microbiology. Thomas, New York.

Haight, F. J. 1942. Coastal currents along the Atlantic Coast of the United States. Coast and Geodetic Survey, Spec. Pub. No. 230, 73 p.

Hardy, C. D. 1970. Hydrographic data report: Long Island Sound, 1969. Tech. Rep. No.4, Mar. Sci. Res. Cent., State univ. of New York, Stony Brook. 44 p.

Hardy, C. D., and P. K. weyl. 1970. Hydrographic data report: Long Island Sound, 1970, Part I. Tech. Rep. No.6, Mar. Sci. Res. Cent., State Univ. of New York, Stony Brook. 50 p.

Hardy, C. D., and P. K. Weyl. 1971. Distribution of dissolved oxygen in the waters of western Long Island Sound. Tech. Rep. No. 11, Mar. Sci. Res. Cent., State univ. of New York, Stony Brook. 37 p.

Interstate Sanitation Commission. 1971. Annual report, 1970. p. 38-46.

Lorenzen, C. J. 1966. A method for the continuous measurement of in-vivo chlorophyll concentration. Deep Sea Res. 13:223-7.

Marmer, H. A. 1935. Tides and currents in New York Harbor. Coast and Geodetic Survey, Spec. Pub. No. Ill.

McCarthy, J. J. 1970. A urease method for urea in seawater. Limnol. Oceanogr. 15:309-313.

McCarthy, J. J. 1971. The role of urea in marine phytoplankton ecology. PhD Thesis, Univ. of Calif., San Diego.

Murphy, J., and J. P. Riley. 1962. A modified single solution method for the determination of phosphate in natural waters. Anal. Chim. Acta 27:31-36.

Newell, B. S. 1967. The determination of ammonia in seawater. J. Mar. BioI. Ass. U.K. 47:271-280.

Remson, C. C. 1972. The distribution of urea in coastal and oceanic waters. Limnol. Oceanogr. 16:732-740.

Richards, F. A., and R. A. Kletsch. 1964. The spectrophotometric determination of ammonia and labile amino compounds in fresh and seawater by oxidation to nitrite, p. 65-81. In: Y. Miyaki and T. Koyma (eds.) Recent researches in the field of hydrosphere, atmosphere and nuclear geochemistry. Maruzer Co., Tokyo.

Riley, G. A. 1952. Hydrography of the Long Island and Block Island Sounds. Bull. Bingham Oceanogr. ColI., 13:5-39.

Riley, G. A. et al. 1956. Oceanography of Long Island sound. Bull. Bingham Oceanogr. ColI., 15:15-46.

63 Riley, G. A. et ale 1959. Oceanography of Long Island Sound 1952-1954. Bull. Bingham Oceanogr. Coll., 17:9-30.

Ryther, J. H., and W. M. Dunstan. 1971. Nitrogen, phosphorous and eutrophication in the coastal environment. Science 171:1008-1013.

Solorzano, L. 1969. The determination of ammonia in natural waters by the phenolhypochlorite method. Lirnnol. Oceanogr. 14:799-801.

Stephens, K. 1967. continuous measurement of turbidity. Deep Sea Res. 14:465-467.

Strickland, J. D. H., and T. R. Parsons. 1968. A practical handbook of seawater analysis. Bull. 167 Fish. Res. Brd., Canada.

Vaccaro, R. F. 1963. Available nitrogen and phosphorous and the biochemical cycle in the Atlantic off New England. J. Mar. Res. 21:284-301.

Vine and Volkmann. 1950. Woods Hole Oceanographic Institution (Unpublished report). Recopied: undersea Technology. 1964. 4(5) :37.

64 APPENDIX

Formulas for Metric and English Unit Conversion

Multiply by Multiply by Length Meters 3.281 0.305 Feet Kilometers 0.53995 1. 852 Nautical Miles Statute Miles 0.8689 1.15 Nautical Miles Kilometers 0.62137 1. 609 Statute Miles

Area Square Meters 10.8 0.0929 Square feet Square Kilometers 0.386 2.5899 Square Statute Miles Square Kilometers 247.1 0.0040 Acres -5 Acres 43560 2.295xlO Square feet

Volume 9 9 Cubic Kilometers 10 10 Cubic Meters Cubic Meters 35.314 0.02832 Cubic feet Liters 0.2642 3.7853 Gallons Cubic Feet 7.48 0.1337 Gallons Cubic Meters 264.2 0.00378 Gallons Acre-feet 1233.48 0.00081 Cub ic Meters

Flow Cubic meters per second 22.82 0.0438 Million gals per day Gallons per minute 1440.0 0.00069 Gallons per day Cubic feet per second 0.6463 1. 547 Million gals per day Cubic meters per second 35.31 0.028316 Cubic feet per second Cubic meters per second 264.2 0.003785 Gallons per second Million cubic meters per 0.723 1. 383 Million gals per day year Cubic meters per day per 684.3 0.0015 Gallons per day per square kilometer square mile

Mass Long Tons 2273 0.00044 Pounds (Avoirdupois) Short tons 2000 0.0005 Pounds (Avoirdupois) Metric Tons 2205 0.00045 Pounds (Avoirdupois) Grams 0.035 28.349 Ounces Kilograms 2.2046 0.4536 Pounds (Avoirdupois) Grams 0.00220 453.59 Pounds (Avoirdupois)

Velocity Meters per second 2.247 0.4470 Statute miles per hour

Meters per second 1. 944 0.5144 Knots (nautical miles per hour)

65 Parts Eer Million Milligrams per liter 1 1 Parts per million Parts per million 8.235 0.1214 Pounds per million gallons

Dissolved OX:igen 62.54 0.0160 Microgram'-oOatoms O Parts per million 2 per liter 31. 25 0.0320 Micromoles O per Parts per million 2 liter Milliliters per liter 1. 428 0.7002 Milligrams per liter

Dissolved Nutrients Microgram-atoms Phosphorus Milligrams per liter p e r liter 0.031 32.26 Phosphorus Microgram-atoms Nitrogen Milligrams per liter per liter 0.014 71. 43 Nitrogen Grams Carbon per square meter Pounds Carbon per per year 8.922 0.1121 acre per year

Time 5 Days 86400 lxlO- Seconds -8 7 Seconds 3.17xlO 3.1536xl0 Years