Porirua Harbour Seminar Series - Pres 3 - GWRC Presentation on Harbour Health

7/29/2019 Porirua Harbour Seminar Series - Pres 3 - GWRC Presentation on Harbour Health

1/27

Porirua Harbour

A sensitive receiving environmentA sensitive receiving environment

Juliet Milne, 21 October 2009


2/27

Outline The harbour is an

estuary Common estuary

issues Monitoring results

Management issues


3/27

Porirua Estuary The harbour is an actually

an estuary Estuaries are sensitive to

a number of issues:

habitat loss

sedimentation

eutrophication (enrichment)contamination

Monitoring & management need to

target these issues


4/27

Sedimentation monitoring site

Recreation monitoring site

Intertidal monitoring site

Subtidal monitoring site

Stream monitoring site


5/27

Habitat loss Broad-scale mapping

of intertidal substrate& vegetation

% cover of mud,

saltmarsh, seagrass,vegetated terrestrialbuffer, nuisance algae

December 2007base-line (5-yearly mapping)

Rushland, Pauatahanui arm


6/27

2007 survey results


7/27

Invasive species

Invasive kelp (Undaria pinnatifida)


8/27

Invasive species

Plastica fizzii

Roadus tyrus

Shoppin trolleri

Roadus conerii


9/27

Sedimentation Sedimentation plates installed in 2007/08

Depth to plates measured annually


10/27

Eutrophication Annual monitoring at 4 intertidal sites

fine-scale sediment condition indicators

benthic (sediment-dwelling) fauna

Annual mapping of macroalgal cover


11/27

Measuring the depth of

oxygenated sediment

Healthy

Anoxic


12/27

Macroalgae cover

Sea lettuce (Ulva)

Eel grass (Zostera)

January 2009 morethan 50% coverageof nuisance algae in

some areas


13/27

Identification of benthic fauna

Cockle

Wedgeshell

Mudflat whelk

Capitella capitata

Polychaete worms

Benthic faunaphotos: Cawthron


14/27

Contaminants Part I

Disease risk

Water quality

tested at 6recreational sitesweekly duringsummer

Not always safe

for swimming

avoid after rain


15/27

1

10

100

1,000

10,000

Jul-2007 Dec-2007 Jun-2008 Dec-2008 Jun-2009

En

terococci(cfu/100mL)

Action guideline

Alert guideline

Paremata Bridge, 2007-2009


16/27

Porirua Harbour rowing club, 2001-2009

1

10

100

1,000

10,000

Nov-2001 Nov-2002 Nov-2003 Nov-2004 Nov-2005 Nov-2006 Nov-2007 Nov-2008 Nov-2009

Ente

rococci(cfu/100

mL)

Action guideline

Alert guideline

unsafe


17/27

Contaminants Part I cont.

Disease risk

Shellfish flesh

(cockles) testedperiodically

Lack of guidelinesfor manycontaminants

Avoid streams &stormwater

outfalls


18/27

Contaminants Part II

Toxicants

Five subtidal

monitoring sitessampled in 2004,2005 & 2008

Lead, zinc & DDTmain contaminants of concern

elevated, persistent & toxic

No clear evidence of significant

ecological effects


19/27

Total zinc concentrations

ANZECC ISQG-low


20/27


21/27

Total DDT concentrations (at 1% TOC)

PAH1 PAH2 PAH3 POR1 POR2

Site

0

1

2

3

4

5

6

7

8

9

10

DDT

(ng/g@

1

%TOC

)

ANZECC ISQG-Low = 1.6 ng/g

ARC ERC:red = 3.9 ng/g

ANZECC ISQG-low

ARC ERC red


22/27

Toxicants-intertidal hotspot study Targeted stream outflows,

and stormwater outfalls

southern end of harbourstreambed sediments

Clear evidence ofstormwater-derivedcontamination

Zinc, lead, PAHs, DDTabove guidelines insurface sediments

Semple St outfall


23/27


24/27


25/27

Management issues

Sensitive receivingenvironment in an

urban setting

Sediment & nutrient

inputs control atsource

Transport ofcontaminants

stormwater-derived

inputs are ongoing


26/27

Management issues

Existing contamination

Future development?

Whole of catchment

approach needed


27/27

Everyonehas a role to play

Porirua Harbour Seminar Series - Pres 3 - GWRC Presentation on Harbour Health

Documents

Transcript of Porirua Harbour Seminar Series - Pres 3 - GWRC Presentation on Harbour Health