FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * Welch Barry Edward   2. Issuer Name and Ticker or Trading Symbol ATLANTIC POWER CORP [AT] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) CEO & President (Last) (First) (Middle) C/O ATLANTIC POWER CORPORATION, 200 CLARENDON ST., FLOOR 25 3. Date of Earliest Transaction (Month/Day/Year) 03/31/2011 (Street) BOSTON, MA 02116 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Share 03/31/2011   A(5)   97,363 (5) A (5) 255,559 D   Common Share 03/31/2011   D(5)   32,454 (5) D $ 15.11 (5) 223,105 D

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Notional Unit

(1)

03/31/2011

A

20,200 (2)

(1)

(1)

Common Share

20,200

$ 0

160,127 (3)

D

Dividend Equivalent Right

(4)

03/31/2011

A

873 (4)

(4)

(4)

Common Share

873

$ 0

161,000

D

Notional Unit

(1) (5)

03/31/2011

M

97,363

(1)

(1)

Common Share

97,363

$ 0

63,637

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Welch Barry Edward C/O ATLANTIC POWER CORPORATION 200 CLARENDON ST., FLOOR 25 BOSTON, MA 02116			CEO & President

Signatures

Patrick J. Welch		05/11/2011
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Each notional unit under the Company's Long-Term Incentive Plan represents a right to receive one-third in cash (net of any applicable withholdings) and the remainder in a fractional common share, or (at the election of the reporting person) one common share, or (at the discretion of the board of directors of the Company) cash only.
(2)	Represents notional units earned (i.e. for which the performance-based hurdles have been met) pursuant to the Company's Long-Term Incentive Plan.
(3)	Excludes 93,959 units previously reported as to which the performance-based hurdles had not been met.
(4)	Represents dividend equivalent rights accrued on the units previously earned pursuant to the Company's Long-Term Incentive Plan. Dividend equivalent rights are credited in notional units. See footnote (1) for economic rights of a notional unit.
(5)	The reporting person settled one-third of 97,363 units in cash and the remainder in common shares.

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